Is preventing a brother from visiting his parents—due to his causing them health and psychological problems, and subsequently severing ties with them—considered a sin that warrants culpability, even though the intention is to protect the parents?

The sister should encourage her brother to maintain ties with their parents, remind him of the rights of piety and kinship, and urge him to contact and visit them, even if infrequently. There is no harm in forbidding him from visiting them if his visits cause them harm. Furthermore, they must maintain ties with their brother and strive to rectify him with gentleness and kindness, and repel his evil with good.