What is the ruling of Islam on a father who rapes children, and what must the mother and children do in this situation?

Rape and child molestation are heinous and grave crimes, among the most egregious of major sins and the most abominable of indecencies. The sons of the deviant man and his wife should advise him and warn him against the wrath and punishment of Allah, but that does not relieve his sons of their duty to honor and treat him with kindness.