No, spouse, his weight loss is not normal at all! :shocked:
Has he simply stopped eating altogether? How does he find the willpower to overcome his hunger pangs? Are you sure he's not taking some drug or "dietary supplement" to help him avoid eating?
I have heard that anorexics often deny that they are too skinny, even when put in front of a mirror. Does your brother recognize that he has a problem, or does he think he looks fine, or that he needs to lose even more weight? If its one of the last two, that could be an indication of anorexia.
What is his spiritual life like? Is he a Muslim? Is he devout? Can you (or have you already) told him that God does not want to be like this, that he is making himself more unattractive to women, and that he needs to avoid extreme behavior like that if he wants to meet a young lady?
Have you or other family members tried introducing him to a young woman? Some young men are very shy and could benefit from the old-fashioned way of parents arranging encounters for their sons and daughters instead of this "meat market" dating system that we have in the modern Western world.