Believe me @45thighs123* if he chose to distant himself from his kids he will do the same to yours. My ex has told every lie in the book to anyone who will listen about how I stop him seeing our children, I have done everything I can to get him to see them, he just can't be arsed.
It's been 2 years now and I have made sure I have kept every email, text etc to show my kids it was not me who alienated him. It's never as they say it is.*
Really, it's NEVER how they say it is? There have been several people who have given examples where the mother has not truly blocked access and the father has been using that as an excuse, and there have also been several examples where the parental alienation WAS real. I would argue that the reason some men use it as an excuse is because it is actually a real and common thing, making the lie believable. There are bad fathers who abandon their kids for no good reasons, and there are bad mothers who do everything in their power to ensure the other parent is alienated. Both are common and entirely real possibilities.
As for "if he chose to distance himself from his other kids he will do the same to yours" - so many have said this now but the statement is missing the obvious. In cases where the parental alienation is real and that is what has led to the situation, there is no reason he would do that to his others kids without similar provocation. It wouldn't concern me because I don't underestimate what genuine, aggressive parental alienation is like. Anyone could eventually learn to live without anyone if there was nothing they could do to get them back, that's the honest truth many find so uncomfortable. There is a grieving process but ultimately most would end up carrying on with their lives, otherwise they'd have to resign themselves to suicidal misery for the rest of it.
People that genuinely go down the parental alienation route, and they DO exist, deserve the same scorn that is applied to "deadbeat dads" on threads like this, the damage they cause is unconscionable and so often excused with "I bet he's just lying and can't be bothered". They are two sides of the same ugly coin.