Meeting his old folks leads to taboo threesome sex because the old timers don't want to be reminded of their youth. As a result, he's uncomfortable and even ashamed. You can easily break this chain by doing the right things and talking to his old timers about his new hobby and how it is exciting for them. You don't have to worry whether he'll like it or not because he will most likely tell you how he feels when you make love to him with his old buddies..