My wife and I kind of had a similar experience (but as the couple). We had wanted to try a 3some and she invited an old roommate to stay with us for the weekend. She knew the reason we invited her...

Anyway, the only advice I can give is this. If anyone is uncertain about it, DON'T do it. Unless everyone is open and ready for it, bad outcomes could result. I'm not talking about being nervous about it. I'm more referring to your choice of the words "its almost kinda creepy too I guess."

Take it slow. If they wanted to do it before and still do, they may want to do it again in the future if you aren't quite ready for it.

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