Shortly after I got married the first time, around my 21st birthday, me and the spouse got wasted on fuzzy navels with a voluptuous red-headed lady friend. I suggested a threesome. Wife said yes. Redhead said yes. We all went to the bed.
The wife passed out and after some tentative moves, me and the redhead started messing around a little bit. The wife woke up...before anything beyond a couple kisses and boob grabs...I did not touch vagina...and freaked. the. fuck. out. On me. Drama drama drama. Drama, drama, drama, drama. Drama, drama, drama, dramarama. Anyway...
We patched it up and moved on. The redhead stayed friends. But I was now "paying" for the botched threesome with quite a bit of angst, sideways comments, sex-withholding and manipulation. Did I mention the wife was pregnant?
After the kid was born, because I liked her as a person, because she was beautiful, because I was nostalgic for a previous redheaded girl, and because I was already getting consequences for making out with her...I fucked the redhead....in a secret twosome. Two or three times. Worth it.
Anyway...I honestly can't remember the circumstances under which I was found out, but it led to a string of revenge adultery by the wife. (Some may have actually happened prior to the actual redhead sex). And then we did what every responsible married adults would do in our situation...we had another baby!!!!
About 3 decent and probably faithful years go by and then I fucked a few waitresses and another family friend, she had an ongoing affair with a really gross bald professor guy that looks like a creepy actor...we separated, got back together, tried for about 6 months to actually work on it and then ultimately faced facts and got divorced! Phew! Only took 10 years total.
TL/DR: No means no but yes doesn't always mean yes. OP's desire for threesome with sexy redhead destroys 10-year marriage before it really even gets going, even though drunk wife sorta agreed. Doesn't matter, had redhead.