Is it obligatory to listen to a father who is full of doubts and ill-conceived notions and who backbites his siblings, or should he be advised, even with the possibility of his anger? And is not going to clean his abandoned house considered an act of disobedience to parents?

The basic principle regarding listening to backbiting is that it is not permissible, and one must object to it, unless a person fears harm, in which case a heart-felt disapproval suffices, along with leaving the gathering if possible. Objecting to parents differs from objecting to others; it must be done gently, without violence or abuse. Taking care of and serving one's father is an obligation upon all children according to their ability, and sometimes being late due to being busy with household duties is not an act of disobedience. Siblings should be advised to cooperate in taking care of their father, for striving to honor one's parents is among the best deeds and the most beloved to Allah.