Guy I’ve seen 3 times wants a 3 some with his best friend (male)

I’ve been dating a guy for almost 5 weeks. Everything was going okay until he started pulling back, no dates, hardly seen each other etc. I noticed he spent 80% of his time with his best mate, which is the reason he didn’t have time for me.

I asked him what was going on, he apologised for being distant, and eventually opened up that he wanted me to have a 3 some with his male friend. He wanted to feel jealous of me with another man, and seemed to get off on the idea of his friend wanting me/ watching us.

This has thrown me off completely as we haven’t been dating long for him trust me with this information, something about it seems like a power move with this friendship I can’t understand.

HELP