Which is a rule we agree with. But when the friend makes herself the swinger, that's a different story.

We're 39F 36M (R & R) couple, that's played on and off through out our relationship.

About 18 months ago, Mrs R befriend one of the teachers 24F (N) at our kids swimming. They've gotten to know each other quite well, platonically. Lots of flirty chat between because that's just how the single girl is.

About 6 months ago, Mrs revealed to her that the two guys N was chatting to at our house warming party (vanilla party) where actually parts of former play couples. Two weeks ago, at N's birthday, she declared (slightly drunk) that Mrs R was next on her to do list.

So last night the girls had time to themselves first, before Mr R joined in. 2.5 hrs later, probably 18 orgasms for Mrs R, and N giving herself five more in the shower while we watched (her period started as they started playing).

This morning the flirting continued, cuddles and kisses for both of us (out of sight of the kids) and they've gone off grocery shopping.

N has declared, and we agree, that last night is a night we'll never forget. Plans are being made for a better timed night where we are all available!

So a friend can become a swinger, but only of it is 100% their idea.