I have been a secret to someone's girlfriend and while it was a bit fun, it was also insensitive to her as well as in the end spoiled our chance at playing it real poly. I will never be a secret again. I am too poly for that
Well, I am a secret to new bf's mom, but that is more of a mutural decition and also we have not been together that long. We are in the process of slowly expanding who knows.