I have a 14 year old son. His 'father' told me to terminate the pregnancy (conceived 8 months into a long distance but full on relationship and tes we were 'careful but no contraception is 100%) and we'd continue our relationship or keep the baby and we were done.
I kept 'the baby'. My ex had no contact for months then I got 'sorry, I miss you' messages etc then he'd be 'sorry I just can't do this' messages.
He came to see his son once when he was led than a year old and the truth came out - he wasn't single when we met. He'd lied endlessly. The flat I'd stayed in multiple weekends wasn't his, it was a friends who was working abroad. He had a 4 year old daughter which I knew about but too but he'd told me he & the little girls mum had split up amicably a year before we net. All lies ...
Anyway, they had now split up and he was moving back to his hometown in London. That's why he'd decided to visit as we were on his way to a visitation weekend with his daughter.
After his curiosity visit it was back to 'I can't do this' again so, I told him he was either in or out and it was his choice.
Couple of years later and he's married and shortly after they have a son.
I am very open and honest with my son about the whole situation. He knows that his Dad has a son and a daughter and I made a point of talking about them because it's healthier for my son to know than to lie to him and one day in his teens him 'find out' anything. I'm doing the right thing for my son. My ex blocked me on fb for years, though now has unblocked me - no doubt when guilt and curiosity get the better of him so I'd occasionally check.out the wife's FB. She seems lovely and I've occasionally been tempted to message her but I never could because that wouldn't be what's best for my son.
But ... the daughters mother has no idea my son exists.
The 'new' wife almost certainly has no idea my son exists.
His daughter now 17/18ish & son 6 have no idea they have a brother.
If my son one day decides he wants to reach out and contact them, I'm not sure how it would be received but, I'll be there to try and support him and steer him through.