Are you turned on by the thought of your s/o having sex with someone else? Most guys would jump at the opportunity to be in bed with 2 women or at least suggest it to their wives. What if your wife came to you and suggested that you have a MMF threesome. How about the swinging scene? Have you ever swapped with other couples and watched each other. I haven't seen my wife with anyone since long before we were married. She was my old gf's best friend and we used to double date.
While at the DriveIn I watched her blow and fu_k several different guys and she watched me with my gf.
I wouldn't mind watching her having sex with another guy ,or woman. She doesn't want to see me with another woman, but she sure keeps asking to see me with our gay friend.