ok I agree that siblings should help their parents with their children, but I'm against them raising or spending most of the time, I'll list the reasons!
1 This will tire you and make your youth tiring and frustrating
2 possible resentment towards parents and siblings
3 Will Make Him Resent Having Children
4 there were cases of people who raised their siblings and were traumatized and did not want to have any more children

So yes, I'm in favor of siblings helping their parents, but it shouldn't be a burden for them.

(You can excommunicate me now!)

1 This will tire you and make your youth tiring and frustrating
2 possible resentment towards parents and siblings
3 Will Make Him Resent Having Children
4 there were cases of people who raised their siblings and were traumatized and did not want to have any more children

I totally agree. There was in the news a story about a traditional catholic boy that was setup by an undercover FBI agent. He had been tasked with caring for an elderly grandmother all by himself. If this burden had not been placed on him more than likely he would have never gone through the trauma with the FBI.  Although daughters are better suited for child care I have seen large families where the older daughters were tasked with caring for younger siblings. They delayed their own marriages because they were not anxious to start families of their own. But in many cases this just can't be helped. Children are obligated to help their parents.

I will respond to your objections
1 I am of Italian descent, yes, I have experience
I met both my own family, as well as other people and friends
2 modern perspective? I know people aged 70 who said it was very difficult to take care of their siblings, isn't it natural? Just ask and see what people say! About the present, I met people who loved their brothers very much, but admitted that it was very tiring to take care of them, they often took care of them all alone! what child would be resentful, I'm sorry to say that you are a person who doesn't know how to read well, donating your time and helping your parents, it's a virtue, but imagine, not being able to rest and barely being able to study because of this task because You are the main responsible ! That's why these are the cases I mentioned!
3 I partly agree with you, but family love also comes from the support of parents and I never said they shouldn't help and again you accuse me of being a heretic !because I don't read well or because you want to accuse me of being a heretic and a modernist for the pleasure of your own ego!
4 saints, in fact, however, remember that parents often had to work and in the case of Saint Therese, there were several older sisters taking care of one, the cases I mentioned were 1 or 2 taking care of several alone and remember- If the church says that the ideal is for parents to raise!
Now I ask you, do you have experience?
Do you live in a Catholic bubble?
Furthermore, you have a very unempathetic and romantic view of the world!
conclusion
I never said that brothers shouldn't help
Children must help their parents and parents must teach their children the virtue of work, both at work and at home.

People who come from families with few children learn the opposite of this.