What is the ruling on a woman who waives her inheritance for her brother willingly, while her children are in dire need of this inheritance, which would secure their future, taking into consideration the potential family problems that might result from this?

It is permissible for a mature woman to relinquish her inheritance to her brother if she sees a benefit in doing so, and no one can prevent her from disposing of her right. This relinquishment does not justify family animosities, and whoever instigates them is blameworthy. The expenses of children are obligatory upon the father, and the mother is not obligated to spend on them except voluntarily. If her children are more in need of money than her brother, she is advised to do so without compulsion. The true securing of a child's future is by raising them in obedience to Allah, for the true future is the Hereafter.