What is the right of brothers to the wealth of their married brother, and is giving them money considered a loan or an obligatory right, like the right of parents, wife, and children?

Alimony for the father is obligatory upon the son if the father is in need. If he is wealthy, it is not obligatory. Alimony for needy parents is obligatory upon all capable children. If the other children are unable or do not spend, then the capable son must spend according to his ability, provided that he finds what he spends in excess of his personal needs. As for alimony for siblings, it is not obligatory unless they are poor and the one spending is their heir. However, it is among the best righteous deeds. Money spent on siblings, if declared as a loan, must be repaid. If it is not declared as such and they are in need, the son can spend on them and intend to seek reimbursement from his father for what he spent, or he can make it a voluntary act on his part.