He should try to ask his wife why she does no tlike their gathering. She might just want to be alone with her family member.
I found out from my wife that even a couple should spend much time together but they need time for themself. My wife alway wanted time to chat with her so called friends, to play games or to watch tv series. I always complained to her but I gave up eventurally. You cannot force your partner to do something she/he does not want to do.