Also known as a commune. Mazel Tov to you and whoever wanders through.
Hope it all works out. But as others have said, both the gay/straight thing and the open thing are potential sources of problems (not necessarily so, depending on the people involved, but they sound like they can be for a significant proportion of those trying them). So just make sure you’re careful about what you get into, leaving open the possibility (however remote) that because it is an unusual situation, it may not work out due to no fault of either of you.
If you do come out with it to family members and they seem disapproving, it may just be that they’re more concerned about there being greater difficulties in making the situation work (in the way that many posters above are) rather than disapproving/judging of the idea in theory. Best of luck though.
“You can go in halfway only, that’s it! We can tattoo a line around the halfway mark”
Heavens above! Sex without love.