Has anyone experienced parental alienation? Did your kids ever come back to you?

Not yet, but once upon a time I was the kid. I came back when I’d done some growing, reclaimed my life autonomously and got some perspective, but also once my parents of their own volition took personal responsibility for how their poor choices/behavior effected me/my path and I could see they’d been making efforts to do better by me and for themselves.

My mother’s side is another story. I make some effort to keep in touch for my daughter’s sake, but she’s never been able to admit to herself the ramifications of her actions in any capacity or made any effort to do better, so I’m mostly cordial to her, but there’s near no relationship there.

Haven't spoken to my dad in a bout 3-4 years. I can't say that i miss him much but i do know he's not in my life. When i became a parent i couldn't help see his failings, and i lost respect for him as a person.

I know it's not exactly what you asked and every situation is different, but i say because like me maybe your kids feel it's your responsibility to acknowledge a failing and make amends.

I have alienated my father. If he wants a relationship with me, he will have to prove that he actually cares and actually make a sustained effort. I owe him nothing. He was a hardly my dad. More just a person who made my life more difficult.

yes and they will come back in due time i believe

...parental...what?