Pius XII helped the Jєωs because he was a follower of Christ, who said, "That which you did for the least of one of these, you did it to me."

All of the children of God are our brothers.

From Pope Pius XI;
8. Whoever exalts race, or the people, or the State, or a particular form of State, or the depositories of power, or any other fundamental value of the human community - however necessary and honorable be their function in worldly things - whoever raises these notions above their standard value and divinizes them to an idolatrous level, distorts and perverts an order of the world planned and created by God; he is far from the true faith in God and from the concept of life which that faith upholds.
http://w2.vatican.va/content/pius-xi/en/encyclicals/docuмents/hf_p-xi_enc_14031937_mit-brennender-sorge.html

From Pope Pius XI;
8. Whoever exalts race, or the people, or the State, or a particular form of State, or the depositories of power, or any other fundamental value of the human community - however necessary and honorable be their function in worldly things - whoever raises these notions above their standard value and divinizes them to an idolatrous level, distorts and perverts an order of the world planned and created by God; he is far from the true faith in God and from the concept of life which that faith upholds.
http://w2.vatican.va/content/pius-xi/en/encyclicals/docuмents/hf_p-xi_enc_14031937_mit-brennender-sorge.html

All of the children of God are our brothers.

All of the children of God are our brothers.

34. Among the many errors which derive from the poisoned source of religious and moral agnosticism, We would draw your attention, Venerable Brethren, to two in particular, as being those which more than others render almost impossible or at least precarious and uncertain, the peaceful intercourse of peoples.

35. The first of these pernicious errors, widespread today, is the forgetfulness of that law of human solidarity and charity which is dictated and imposed by our common origin and by the equality of rational nature in all men, to whatever people they belong, and by the redeeming Sacrifice offered by Jesus Christ on the Altar of the Cross to His Heavenly Father on behalf of sinful mankind.

36. In fact, the first page of the Scripture, with magnificent simplicity, tells us how God, as a culmination to His creative work, made man to His Own image and likeness (cf. Genesis i. 26, 27); and the same Scripture tells us that He enriched man with supernatural gifts and privileges, and destined him to an eternal and ineffable happiness. It shows us besides how other men took their origin from the first couple, and then goes on, in unsurpassed vividness of language, to recount their division into different groups and their dispersion to various parts of the world. Even when they abandoned their Creator, God did not cease to regard them as His children, who, according to His merciful plan, should one day be reunited once more in His friendship (cf. Genesis xii. 3).

37. The Apostle of the Gentiles later on makes himself the herald of this truth which associates men as brothers in one great family, when he proclaims to the Greek world that God “hath made of one, all mankind, to dwell upon the whole face of the earth, determining appointed times, and the limits of their habitation, that they should seek God” (Acts xvii. 26, 27).

38. A marvelous vision, which makes us see the human race in the unity of one common origin in God “one God and Father of all, Who is above all, and through all, and in us all” (Ephesians iv. 6); in the unity of nature which in every man is equally composed of material body and spiritual, immortal soul; in the unity of the immediate end and mission in the world; in the unity of dwelling place, the earth, of whose resources all men can by natural right avail themselves, to sustain and develop life; in the unity of the supernatural end, God Himself, to Whom all should tend; in the unity of means to secure that end.

39. It is the same Apostle who portrays for us mankind in the unity of its relations with the Son of God, image of the invisible God, in Whom all things have been created: “In Him were all things created” (Colossians i. 16); in the unity of its ransom, effected for all by Christ, Who, through His Holy and most bitter passion, restored the original friendship with God which had been broken, making Himself the Mediator between God and men: “For there is one God, and one Mediator of God and men, the man Christ Jesus” (I Timothy ii. 5).

40. And to render such friendship between God and mankind more intimate, this same Divine and universal Mediator of salvation and of peace, in the sacred silence of the Supper Room, before He consummated the Supreme Sacrifice, let fall from His divine Lips the words which reverberate mightily down the centuries, inspiring heroic charity in a world devoid of love and torn by hate: “This is my commandment that you love one another, as I have loved you” (Saint John xv. 12).

41. These are supernatural truths which form a solid basis and the strongest possible bond of a union, that is reinforced by the love of God and of our Divine Redeemer, from Whom all receive salvation “for the edifying of the Body of Christ: until we all meet into the unity of faith, and of the knowledge of the Son of God, unto a perfect man, unto the measure of the age of the fullness of Christ” (Ephesians iv. 12, 13).

42. In the light of this unity of all mankind, which exists in law and in fact, individuals do not feel themselves isolated units, like grains of sand, but united by the very force of their nature and by their internal destiny, into an organic, harmonious mutual relationship which varies with the changing of times.

43. And the nations, despite a difference of development due to diverse conditions of life and of culture, are not destined to break the unity of the human race, but rather to enrich and embellish it by the sharing of their own peculiar gifts and by that reciprocal interchange of goods which can be possible and efficacious only when a mutual love and a lively sense of charity unite all the sons of the same Father and all those redeemed by the same Divine Blood.

44. The Church of Christ, the faithful depository of the teaching of Divine Wisdom, cannot and does not think of deprecating or disdaining the particular characteristics which each people, with jealous and intelligible pride, cherishes and retains as a precious heritage. Her aim is a supernatural union in all-embracing love, deeply felt and practiced, and not the unity which is exclusively external and superficial and by that very fact weak.

45. The Church hails with joy and follows with her maternal blessing every method of guidance and care which aims at a wise and orderly evolution of particular forces and tendencies having their origin in the individual character of each race, provided that they are not opposed to the duties incuмbent on men from their unity of origin and common destiny.

46. She has repeatedly shown in her missionary enterprises that such a principle of action is the guiding star of her universal apostolate. Pioneer research and investigation, involving sacrifice, devotedness and love on the part of her missionaries of every age, have been undertaken in order to facilitate the deeper appreciative insight into the most varied civilizations and to put their spiritual values to account for a living and vital preaching of the Gospel of Christ. All that in such usages and customs is not inseparably bound up with religious errors will always be subject to kindly consideration and, when it is found possible, will be sponsored and developed.

47. Our immediate predecessor, of holy and venerated memory, applying such norms to a particularly delicate question, took some generous decisions which are a monument to his insight and to the intensity of his apostolic spirit. Nor need We tell you, Venerable Brethren, that We intend to proceed without hesitation along this way. Those who enter the Church, whatever be their origin or their speech, must know that they have equal rights as children in the House of the Lord, where the law of Christ and the peace of Christ prevail.

48. In accordance with these principles of equality, the Church devotes her care to forming cultured native clergy and gradually increasing the number of native Bishops. And in order to give external expression to these, Our intentions, We have chosen the forthcoming Feast of Christ the King to raise to the Episcopal dignity at the Tomb of the Apostles twelve representatives of widely different peoples and races. In the midst of the disruptive contrasts which divide the human family, may this solemn act proclaim to all Our sons, scattered over the world, that the spirit, the teaching and the work of the Church can never be other than that which the Apostle of the Gentiles preached: “putting on the new, (man) him who is renewed unto knowledge, according to the image of him that created him. Where there is neither Gentile nor Jєω, circuмcision nor uncircuмcision, barbarian nor Scythian, bond nor free. But Christ is all and in all” (Colossians iii. 10, 11).

49. Nor is there any fear lest the consciousness of universal brotherhood aroused by the teaching of Christianity, and the spirit which it inspires, be in contrast with love of traditions or the glories of one’s fatherland, or impede the progress of prosperity or legitimate interests. For that same Christianity teaches that in the exercise of charity we must follow a God-given order, yielding the place of honor in our affections and good works to those who are bound to us by special ties. Nay, the Divine Master Himself gave an example of this preference for His Own country and fatherland, as He wept over the coming destruction of the Holy City. But legitimate and well-ordered love of our native country should not make us close our eyes to the all-embracing nature of Christian Charity, which calls for consideration of others and of their interests in the pacifying light of love.

50. Such is the marvelous doctrine of love and peace which has been such an ennobling factor in the civil and religious progress of mankind. And the heralds who proclaimed it, moved by supernatural charity, not only tilled the land and cared for the sick, but above all they reclaimed, moulded and raised life to divine heights, directing it toward the summit of sanctity in which everything is seen in the light of God. They have raised mansions and temples which show to what lofty and kindly heights the Christian ideal urges man; but above all they have made of men, wise or ignorant, strong or weak, living temples of God and branches of the very vine which is Christ. They have handed on to future generations the treasures of ancient art and wisdom and have secured for them that inestimable gift of eternal wisdom which links men as brothers by the common recognition of a supernatural ownership.

51. Venerable Brethren, forgetfulness of the law of universal charity — of that charity which alone can consolidate peace by extinguishing hatred and softening envies and dissensions — is the source of very grave evils for peaceful relations between nations.

11.

(. . .)

But see, even now, it is said, we love one another. For one man has two friends, and another three. But this is not to love for God's sake, but for the sake of being beloved. But to love for God's sake has not this as its principle of Love; but such an one will be disposed towards all men as towards brethren; loving those that are of the same faith as being true brothers; heretics and Heathen and Jєωs, brothers indeed by nature, but vile and unprofitable — pitying and wearing himself out and weeping for them. Herein we shall be like God if we love all men, even our enemies; not, if we work miracles.  For we regard even God with admiration when He works wonders, yet much more, when He shows love towards man, when He is long-suffering. If then even in God this is worthy of much admiration, much more in men is it evident that this renders us admirable.

Chapter 134. The marriages of Jacob are a figure of the Church.

Justin:

If, then, the teaching of the prophets and of Himself moves you, it is better for you to follow God than your imprudent and blind masters, who even till this time permit each man to have four or five wives; and if any one see a beautiful woman and desire to have her, they quote the doings of Jacob [called] Israel, and of the other patriarchs, and maintain that it is not wrong to do such things; for they are miserably ignorant in this matter. For, as I before said, certain dispensations of weighty mysteries were accomplished in each act of this sort. For in the marriages of Jacob I shall mention what dispensation and prophecy were accomplished, in order that you may thereby know that your teachers never looked at the divine motive which prompted each act, but only at the grovelling and corrupting passions. Attend therefore to what I say. The marriages of Jacob were types of that which Christ was about to accomplish. For it was not lawful for Jacob to marry two sisters at once. And he serves Laban for [one of] the daughters; and being deceived in [the obtaining of] the younger, he again served seven years. Now Leah is your people and ѕуηαgσgυє; but Rachel is our Church. And for these, and for the servants in both, Christ even now serves. For while Noah gave to the two sons the seed of the third as servants, now on the other hand Christ has come to restore both the free sons and the servants among them, conferring the same honour on all of them who keep His commandments; even as the children of the free women and the children of the bond women born to Jacob were all sons, and equal in dignity. And it was foretold what each should be according to rank and according to fore-knowledge. Jacob served Laban for speckled and many-spotted sheep; and Christ served, even to the slavery of the cross, for the various and many-formed races of mankind, acquiring them by the blood and mystery of the cross. Leah was weak-eyed; for the eyes of your souls are excessively weak. Rachel stole the gods of Laban, and has hid them to this day; and we have lost our paternal and material gods. Jacob was hated for all time by his brother; and we now, and our Lord Himself, are hated by you and by all men, though we are brothers by nature. Jacob was called Israel; and Israel has been demonstrated to be the Christ, who is, and is called, Jesus.

5. The natural tendency of man to association has never been stronger, or more earnestly and generally followed, than in our own age. This is not at all to be reprehended, unless when so excellent a natural tendency is perverted to evil purposes, and wicked men, banding together in various forms of societies, conspire “against the Lord and against His Christ” (Ps ii., 2). It is, however, most gratifying to observe that pious associations are becoming more and more popular among Catholics also. They are frequently formed; indeed, all Catholics are so closely drawn together and united by the bonds of charity, as members of one household, that they both may be and are truly styled brethren. But if the charity of Christ be absent, none may glory in the name and fellowship of brethren. So wrote Tertullian long ago in pungent words: “We are your brethren by right of a common mother, nature, yet are ye less than men, because unnatural brothers. How much more justly are they called and esteemed as brethren who acknowledge one and the same Father, God; who have drunk in one and the same spirit of charity; who have been borne from one and the same womb of ignorance into the one light of truth?” (Apolog. c. xxxix.)