What is the ruling on praying behind an Imam who severs ties of kinship, and is it advisable to change mosques if praying behind him is permissible?

Severing kinship ties is a major sin, and Allah has cursed its perpetrator. Whoever severs kinship ties, Allah severs him. One who severs kinship ties is a transgressor (fasiq), and the ruling on praying behind him is the same as praying behind any transgressor: it is permissible and valid according to the majority of scholars, though praying behind him is disliked. It is better to seek someone else for imamate, or to advise him to repent. If that is not possible, then it is preferable to pray in another mosque behind a righteous imam. However, if you do pray behind him, the prayer is valid, though disliked.