Mighty - something Ur said - the person we thought we could count on most in the world. I have come to realise that part of their panic stricken behavior is that they know they have ceased to be that person.
Chose not to be, were driven not to be, however we put it, but for all their bluster, they don't like what they have done to us. There is, stuffed deep down, guilt, shame and eventually, I think, remorse. Even if they never show it to us. It eats at them. They know they can't be relied on.
Your xh is doing what my xh did - pursuing the children, and trying to 'make' them have a relationship. Will not see that these things, once given freely out of love, have to be earned again. Again they know this deep down, but will not acknowledge it.