How does a 4 year old who's dad visits him every day confuse him with another man? Are you as present as you say, or you show up and spend your time talking to your ex, judging her choices etc. I never confused my absent dad to any of my mum's boyfriends. Everytime I saw my dad his priority was me, I have never seen him giving attention to his ex wife (my mum) or anyone we meet on street, his only priority was to be dad spending time with daughter. And I only saw the man couple of times in my first decade of life. If you visit daily, I assume you live separately. Is there a reason you can't offer to take the son to your place for the night when mum has a date? Could you not compromise when she has a date, since it makes you uncomfortable to have your child in the house with mum and her guest, then you should happily take the extra quality time on offer with your child.

I agree, my father moved out of town before he found out my mother was pregnant, but he bussed over an hour every weekend, then drove when he got a car, and I spent every other weekend with him once I was old enough for such long times away. even child support he set up to pay extra when he could. I never had the question who my real dad was even if he wasn't around for a month due to certain work seasons.