My son is bi but he wants to marry a woman and have biological children. His husband is a bit hurt about this. How can we navigate this?

So my son and his husband have been dating for 5 years and been married for 2 years. My son has been to therapy for a while and the therapist decided he is actually bi. He has been open with his husband about his bisexuality but his husband is a big bi skeptic and doesn’t believe my son is bi. Then a few months ago my son realized he actually wants to have an affair and the therapist says that this is a emotional affair and my son is pining for a woman. He eventually wants to leave the marriage and start dating women. They are currently in marriage counseling but it doesn’t seem to help. My son just wants to marry and have his own kids. What do we do in this case? How do we make this transition? I am not happy about my gay son leaving his gay husband for a straight life but if it is what he wants then that is what happens.