Should my boyfriend and I have a threesome with another girl and what are reasonable boundaries?

Anonymous
My boyfriend and I have been together for over 3 years now and lately we've both had the fantasy of a threesome with another girl. He's told me he's been into this for a while now as he thinks it's hot imagining me with another girl and I have slowly caught on too as we discuss it quite often now. He doesn't care what the boundaries are whether he can just watch to being fully part of it. He respects whatever my decision is and has left it up to me on what my boundaries for him would be. Since he is the one who wants to see me with another girl, he doesn't need boundaries for me as I am happy to just do whatever I'm feeling with her, whereas I want him to also be involved so I have to think of where my limit is with what him and this third girl can do to eachother. Let me know your thoughts on if having a threesome even is a good idea and if so, what are some reasonable boundaries. Thanks! :)
Should my boyfriend and I have a threesome with another girl and what are reasonable boundaries?
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