I still think he's her biological father

As you may know, my father and I have no relationship at all. He still thinks I’m 12 and still bad mouths my mother when he speaks to me. He’s on some heavy shit now and I’m kind of worried that he won’t make it to his 50s, but I still can’t get over the fact that he literally DOES NOT care about his children. 

I was wondering how it’s going to be when my baby doesn’t know her or his own biological grandfather, how I can’t trust him around myself because I remind him too much of my mother, how there’s no way I’d ever be able to trust him around my baby. It’s sad, really. 

I mean, the baby’s going to have a golden grandfather (my step-dad) and all is going to be well, because they will know him as “Pa-pa.” And it’s going to be great. But still, my own father can’t be part of my life let alone my kids’ lives. 

I’m just in a sulky mood right now.