Partner is calling their meta "our partner" and im not sure how to feel about it

Me and my 2 partners im referring to all went to the same highschool together, I've been dating Aspen since then so Birch knew us as partners before years later we reconnected and fell in love too.

Since starting this relationship, both Aspen and Birch have stated to me that they found the other really attractive. Maybe this is my fault but I decided to tell the two of them that the other said that. Aspen also lives a state away right now though and Birch has expressed that they are not into LDRs whatsoever so has no plans to pursue Aspen at least until someone moves closer. Aspen knows this. But recently They have started calling Birch "our boyfriend". Whenever they say it I remind them "he's my boyfriend, he just thinks you're cute" and the likes, but then they say "well I'm going to be dating him at some point anyway", and idk it just has been rubbing me the wrong way.

Like I get that we're all close and that there are feelings there, but I just can't get over it. It's like, I put in the effort to reconnect either Birch, we had a really beautiful growing period of hanging out and slowly realizing how much we want to be together. We have our relationship pressure points and tiffs that we have worked through to get us to where we are. And it feels like Aspen thinks they can skip over that whole thing straight to us being a triad, which we aren't at this point at all and I guess it also feels dismissive of Birch's feelings and where he is coming from.

I don't want to hurt Aspen's feelings, I feel like I've been pretty direct I telling them that currently only I am dating Birch and that he is not their boyfriend, so I don't know what to say without sounding/feeling like an asshole. What should I do? Thanks folks of reddit in advance