I hope it ends happily too.
The girlfriend of a best friend once said the same. It didn't. I agreed to have a MFM three way with them. She had heard the rumors of my size and had seen my bulge in swim trunks. Very little contact happened between he and I--arms & legs mostly. Both were agog over my size. It was crazy fun made more so because of close friendship.
Things went south after she expressed interest in doing it again. He became extremely jealous. Despite her optimism no amount of apology from she or I soothed his sexual jealousy.They broke up and I lost both as good friends.
After that sex with close friends was off the menu.
They weren't married but we all thought they would be and should be. Forty years later I still wince each time I think of what happened between us--and what I helped destroy.
I see why more people choose to just stay single these days
^This. So many have cheated with me from youth I am surprised anyone chooses to marry. I was optimistic enough to get engaged three times when I was young but accepted they would cheat on me. Why wouldn't I when I cheated on them. One cheated on me. I found out later another did too.
It's just the way humans are. Our species does not instinctually form exclusive lifetime pair bonds. Even short/mid-term ones are a challenge.
A cautionary tale for your consideration.