Hmm. I met Curly's exes--a couple--shortly after we began dating. She was active in the SCA, as were they, and I got involved when we got together. I didn't feel odd about it, though I suspect they did.
She got involved with another couple for a time, though I'd met them prior to her involvement. We've spent a couple of Thanksgivings at their place.
She's mentioned having a man at work flirt with her a bit. If something comes of that, then I'll be able to meet somebody she's involved with after the beginning of said involvement and before it ends.