Is it permissible for a mother to divide her wealth and disinherit her addicted son, and is it permissible for her to divide her wealth between her grandchildren (her son's children) and her daughter?

A person can divide their inheritance during their lifetime as a gift (hibah), and they must be just among their children, giving the male twice the share of the female. It is not permissible to favor one over another in a gift or to bequeath the deprivation of an heir. Your husband's mother can divide her wealth between her son and daughter and give gifts to her grandchildren, but she must not deprive her son of a gift if she gives one to her daughter.

If she wishes to divide it, she may stipulate to her son that he use the money to buy an apartment for his children. This is permissible in a gift if the intention is clear; otherwise, it is not obligatory. If she fears he will not abide by her condition, she should not give it to him. There is no sin upon her if he uses the money for unlawful purposes after owning it.

There are three prohibitions: favoring one over another in a gift, bequeathing deprivation from inheritance, and giving money with the intention of depriving the son (circumventing the inheritance). Fleeing from Allah's rulings through tricks that lead to invalidating rights is not among the ethics of believers.