Playing with a friends brother

This is an odd question so looking for advice. I am a bi married man. Wife had a best friend from HS who lives in another city that we don't see very often. I am sure he is gay. No interest in him . He has a brother a few years younger who has just moved into our neighborhood. He is recently widowed no children. There is a third brother who used to live in town and while he was here I hooked up with him several times either alone or in a 3 some. He did/does not know that I know his brothers. To complicate things we were talking once and he said that his widowed brother used to suck him off daily when they were teens until he met the woman who would be his wife when he was a senior in HS.

I am guessing once a cocksucker always a cocksucker lol. Also had to wonder over the years they would host foreign exchange students- always male. Last one came back to visit for a month during a college break. Very twink very handsome kid but to travel 1000 miles to visit a host family ? And this was after the wife had died.

So what this is leading to I am somewhat interested in finding a FWB and this guy is within walking distance. How do I approach the subject without having him be offended if not interested. Don't want to out either of us or make any awkward situation.
Any suggestions?
Don't want older or younger brothers to ever find out if we do start something!