Is the person who asks this question sinful if he reduces his visits to his mother, who mistreats him and asks him to give up his right to inheritance, in order to avoid problems and the mistreatment of his siblings?

Your deceased father's wealth is a right for all heirs, based on the Almighty's saying: "Allah instructs you concerning your children: for the male, what is equal to the share of two females," and the Hadith (definition): "Whoever leaves behind wealth, it is for his heirs." It is not permissible to harm any of the heirs when dividing the inheritance. As for the mother's actions of injustice, cursing, and reviling, these are strange and cause Allah's displeasure. It is advised to be patient with her and supplicate for her guidance and repentance, and to try to understand the reasons for her displeasure and address them, while being careful not to commit disobedience towards her. You must maintain ties of kinship with her according to custom, and visiting is not obligatory if harm is feared. It is possible to reduce visits while ensuring other means of maintaining ties.