Is it permissible to sever ties with my brother who believes his wife's false accusations against us, and then proceeds to insult and curse us based on that?

It is advisable to speak to the brother's wife directly, or to mediate through someone who can speak to her, counseling her to fear Allah and beware of causing discord. The brother is also advised to honor his parents, maintain kinship ties, and verify any information he receives about his family. Severing ties must be abandoned, and great care must be taken to maintain kinship, for the one who maintains ties is not he who reciprocates, but he who, when his kinship is severed, connects it. It is also advisable to strive diligently in reconciling everyone, due to the immense reward therein, for reconciling disputes is better than the degree of fasting, prayer, and charity.