Is it permissible for a father to stop helping his mentally ill uncle due to the stepmother's mistreatment of the uncle?

If the father is well-off and the assistance does not harm him, he should continue to help his uncle and strive for his uncle to benefit from what he pays, either by advising the uncle's wife, or providing a maid while observing the Islamic regulations, or washing the uncle's clothes. Maintaining kinship ties is one of the greatest acts of righteousness. The Prophet, peace and blessings be upon him, said: "Whoever wishes that his provision be expanded for him and his life span be extended, let him maintain his ties of kinship." (Agreed upon). Maintaining ties with the uncle is obligatory, for he is in the position of a father.