I'm putting a second edit here. This issue is resolved. No need to tell me more about how you think I'm being a bad partner to Archer, I get it already. I know how to move forward now and be a better partner to him in future.

Hi everyone

I'm worried about my boyfriend (I'll call him Archer). I love him and want want what's best for him. I'm concerned that my presence in his life might not be good for him. He's been only with me since we started our relationship about 4 years ago and it's been long distance about 2 and a half years of that.

I have another partner (my nesting partner who I'll call Leo) who I live with and coparent our young child together with. Leo doesn't like Archer for reasons I'm not going to go into.

Anyway, recently Archer said he was thinking about moving closer to where I live. While Archer does have some family here, I worry he is moving nearer me for me primarily though. I don't feel like I can do any relationship escalator stuff with Archer and feel he'd benefit from finding a nesting partner. I have suggested this to him and, while he's been open to the idea of other sexual partners, he seems resistant to another romantic partner.

Myself and Leo have been together for almost 20 years. We did agree before becoming polyamorus that other partners could move in and all that comes with that if we had a house where that was viable. The limits were that everyone had to get along though and that no one (romantic or platonic) was allowed in the house if it would damage anyone's mental health. Additionally, they would also have to be people that myself and Leo considered safe around our child.

While Archer stayed to help me with minding my child when Leo was away on a business trip (Leo knew and was ok with that), that's not the same as everyone living in the same house. Additionally, at that time I had post natal depression and Leo thought it was best to have someone around who knew how to care for young children.

If you've read this far, thank you for reading. I don't know if I'm being silly or not. I hope I'm just overthinking and worried for no reason

*Edited to add: I understand what's going on for me now and how to talk to Archer about it. Thank you to everyone who responded and thank you for the help I received *