I'm in a quad and very involved with both halves. Mr. Fuse and the other husband are both straight. I suppose your question doesn't really apply to me, but I'll answer anyway
. I've been in threesomes (just talking sex here) where I wasn't involved with the other woman. It is SO much better when everyone is attracted to everyone else, that I would barely consider going back and having a threesome where I wasn't attracted to the other woman.