Wa `alaykum as-Salamu wa Rahmatullahi wa Barakatuh.
If what you allege about the man’s father is true, then he ought to do his best to protect his wife against the predatory nature of his father. He is justified in keeping her at a distance from him. One of the rules of Islamic jurisprudence states: “Where there is harm, it ought to be removed.”
Therefore, if he cannot trust his father in regards to his wife, he is justified in keeping her away from him for her protection.
However, while doing so, he should still keep good relations with his father in all other matters. He should also pray to Allah to guide him to see the harm he is inflicting on himself and others through his immoral behavior.
Almighty Allah knows best.
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