I have romantic and sexual feelings for two people currently. One is my boyfriend and the other is my ex-girlfriend. My ex-girlfriend is also one of my best friends, and we hook up some times with permission from my boyfriend. All three of us are polyamorous to some extent. I have strong feelings for both of them, and would love to be in a relationship with both. However, I've discussed the topic with my boyfriend before (a couple of months ago), and he has stated that he'd rather I be in a relationship with someone he also had feelings for or at least got along with better than he gets along with my ex-girlfriend. They have only met once, and my ex told me she thought I could do better, somewhat jokingly. This rubbed my boyfriend the wrong way, and he doubts there's any way that they'll be at a point where he is comfortable with me being in a relationship with her.

I think part of the problem is that I'm seeing the potential relationship as more of a line (x dating y who is also dating z, but x and z are not dating) while he's seeing it as more of a triangle (x, y, and z are all dating). I'm also hesitant to try to get them to spend more time together, because I fear that they will have worse opinions on each other because their interactions will be colored by the fact that they got off on the wrong foot originally.

I want to bring up the subject again, but I don't know how to without disrespecting his wants. I understand that if we add someone else into the picture, he wants to be happy and satisfied with his relationship with that person as well. He does not seem to mind our current arrangement, where I am free to hook up with my ex as long as I ask him before or tell him right after, but I don't necessarily want my ex to remain my "fuck buddy" when I have stronger feelings than what typically comes with that. I don't know if I should try to explain this to him or let it be and just accept that this is what the relationship is and will be for some time.

Any advice?