How to tell my bf I have a FP?

Okay, I know that ‘FP’ is a bad term but I don’t know what else to call them, my obsession maybe? I am not sure… ANYWAY I (18f) have BPD, and my boyfriend (19m) knows about my symptoms and knows about “favourite people”. We have been together a little over a year now and my last obsession was HIM so I haven’t had one since.

I recently met one of my friends (online) after 8 years a few days ago and I see him as my brother but he has definitely turned into my ‘FP’.

The problem is that my boyfriend is already jealous over this friend and has told me he doesnt mind me talking or meeting with him but he does get a little jealous, I dont have any feelings towards my friend but I feel like telling him he’s my FP will probably crush him a little. Any tips on how to tell him? 😭