My FWB joking asked if I would let him and his brother tag team me. I'm supposed to be visiting them later this month, and open to trying this. What's the best way to approach his brother? Any favorite mmf positions?

Edit: Why the hate though? My fwb and I know we won't work out long-term and are just having fun. Obviously, his brother looks like him so I'm not complaining. The dynamic and repercussions between them afterwards is not my problem. I'm 30, they are 27 and 24.