Would the questioner be sinful for leaving some of her father's care to her brother and his wife, given that she is his only daughter and he is ill, due to his preference for her brother and his family over her and her children, and his disregard for her children's needs, knowing that she is the one primarily providing him care, and the father gives all his money to her brother and his wife, with half of this money coming from her deceased mother's pension?

A father must be equitable among his children in gifting, and it is not permissible for him to favor some over others without a legitimate reason. It is not permissible for a father to deprive his daughter of her legal right to her deceased mother's inheritance, nor to dispose of it except with her full consent. Sons and daughters alike must care for and be dutiful to their father and serve him; this is an equal duty for both, not for one over the other. A son's wife is not obligated to serve her husband's parents, but if she does so, it is a praiseworthy act for which she will be rewarded.