Male cat help

I’m at my wits ends.. Idk what to do anymore, for context

I have a 1 year old male cat, a 3 year old female cat and another almost 1 year old female cat, we’ve had my male cat since he was a kitten, and my eldest female cat since she was 1, and got my male cat desexed at 6-8 months, but even after he will not stop peeing, and it reeks, it’s everywhere, it got to the point where we had to give him away, but then the person we gave him to lost him and didn’t give a flying Eff about him, so we ended up finding him and brought him back, and once again.. pissin everywhere.. we have tried almost anything, the Vet we found him at says he’s perfectly healthy .. we’ve booked him in to see another vet just to confirm he’s okay.
When it was just him and the eldest we had two kitty litters, and now we have three but - I’ve even tried scenting his areas with a sock..
HELP 😀😭