How can one deal with a brother who accuses his sisters of neglecting their parents, and incites his wife, who creates problems, against them, while the father believes that this is just the brother's nature and should be ignored?

Filial piety is one of the greatest causes for Allah's pleasure, and disobedience to parents is one of the gravest sins. If parents need service and care, it becomes obligatory upon all children. If they do not need it, then that obligation is lifted from the children.

One must strive in showing filial piety to parents and cooperate in serving and caring for them. If a brother's wife undertakes the care of the parents, she deserves thanks. As for the brother's misconduct, he should be advised while observing his right to kinship ties, because maintaining kinship is obligatory even towards those who sever it. Responding to evil with good brings affection and repels the evil of Satan, in accordance with His, the Almighty's, saying: {Nor can a good deed and a bad deed be equal. Repel [evil] with that which is better, and thereupon the one whom between you and him was enmity will become as though he was a devoted friend.}