XP stayed out of DD1's life for years - his choice - & has recently attempted to re-establish a relationship.
The problem is, she is now 14 & he is a stranger to her. She doesn't feel comfortable alone with him, but he doesn't understand - to him, he is her 'daddy' and he can't work out what the problem is. He thinks it's us
DH has been in her life since she was 11 mths old & he is her dad & always will be, whether we are together or not. He tells her he fell in love with her before me so she is lucky to have had that in her life.

My mum left me with my dad when I was 2 and a half, moved interstate. I did get to see her over the years but when I had my own children it hit me like a ton of bricks that she had up & left me, moved away - I could NEVER do that to my kids. So yeah I have had a bit to deal with (still am )
But I see it as part of my life's journey, I guess, we all have things to deal with & lessons to learn... these are mine.

It's normal to feel hurt for our children... but it's not the end of the world for them. There is still plenty of love in the world
I hope you find peace