Please listen to the ladies here who have told you to keep out of it. I will add myself to this very same choir.
My DDs biological father is an absolute scum waste of space. Absolute. He refused to work when I was pregnant. He bought a pack of two body suits total for our daughter. And one packet of nappies. He wasn't involved with anything. For example, he never changed a nappy, he never gave her a bottle, never ever did a night feed. Nothing. The cards we were given when she was born, had money in. He took that and spent it on himself.
The drained my bank account.
When we split up he ran away with her. He introduced his new girlfriend as her new mummy when she was 3 months old.
He didn't pay a penny CM until she was 3 1/2 years old. He paid £25 which came to me irregularly. I went to CSA he quit his a job so he didn't have to pay.
When he got married, DD became unhappy to go to his place, which he blamed on me. I became aware some time later the new wife was abusing my DD. They made her call new wife mum. New wife would slap DD around the face. They would spend weekends trying to get her to say it was me and my partner who were hurting her. They accused me of beating DD to the nursery, they called social services and made accusations against my partner.
When these plans backfired they tried to convince DD that at the age of four how much fun it would be to go and live with them, even moved so she could have her own room.
But wouldn't buy her birthday or Christmas Day presents or cards. And decide to just not show up when they wanted... I was controlling because I wanted him to stick to a contact order!
He would phone me up to 9 times a day.
It doesn't sound like a lot, but on top of all this, he would tell people the most horrific lies about me. I was apparently letting DD call every new man Dad, I apparently had a dog who would shit all over my carpets and I wouldn't clean it. I made him sleep with me so I would allow him to see DD. He told his wife I was having a mental breakdown, or was too drunk to look after DD as an excuse to run off over night (honestly! Never ever been on that kind of stage, even if I were, I wouldn't have Called him) he also told her DD was in hospital after a nasty accident because I'd not been watching her properly and he stayed up the hospital all night with me (nope! Never happened!) there were loads of other lies that I'm sure I don't know about, but I was the devil to anyone who knew him. I knew this because he got his girlfriends dad/sister to pick up DD a lot, he didn't drive and couldn't afford bus.
For good measure I became aware that he didn't even have a car seat (1 hour drive!)
My point is, you've no idea what he's really like, what he may of put her through, what she may have to go through because of your involvement. OR, most importantly what this could do to his child.
If he believes that his step dad is his dad, who are you to shatter that sense of family he has?
Very rare is there a woman who's child doesn't see their dad for no reason at all... many of us feel like shit because of it.