What is the religious ruling on a maternal uncle cutting ties with his sister's children and refusing to visit them after their mother's death, despite attempts at reconciliation?

It is not permissible to boycott one's maternal uncle, even if he boycotts, and it is obligatory to maintain ties with him, as the Prophet, peace and blessings be upon him, said: "There is no obedience to a creature in disobedience to the Creator."