Is the family sinful for disowning a relative and completely severing ties with him, while he is aware of and condones his wife's illicit actions and her giving birth to illegitimate children?

A man's acknowledgement of indecency among his household is a great sin called dayyāthah (cuckoldry or pimping). In the Hadith, it is stated: "A dayyūth will not enter Paradise." It is incumbent upon his family to advise and warn him, and to ostracize him if he persists in sin, provided that doing so achieves a benefit; otherwise, they should not ostracize him. His children must honor and treat him kindly, even if he persists in his transgression, because a father's transgression does not negate his right to filial piety. The children of a woman are attributed to the man, and they have their rights unless he denies them through liʿān (oath of condemnation). His relatives do not have the right to deny the children of his wife.