Yic
I didn’t understand your story completely. Your friend got married and has to follow whatever his wife’s family tells him to do?
I think if you have concerns you can voice them, but be careful. Ask him how he’s doing and just point out what you notice (that he’s out of touch with everyone). Let him respond. Don’t voice your own opinion about whether you think it’s ok or not without asking a rav or an organization like shalom task force. He might not mind pulling away socially, but if you tell him you think it’s not ok, he might re-think his own perspective and that can start shalom Bayis issues.