You lost your family 20 years ago. Your dad has made no effort to see you and ease his conscience on his death bed because he feels no remorse. You can choose to let it go if you understand forgiveness and closure in this fashion, but you will not get closure from him.
And because of that, when he dies you will suffer complicated grief. You'll mourn the dad that you loved as a small child and you'll mourn the dad that he never was for you as a teenager and an adult.
So, cry and mourn and mourn and cry. Take all the time you need. Probe gently to find out whether your mother was just under his thumb and whether she's willing to start building some type of relationship with you and your kids.
We can't make it better, but we can be here for you, and we will be.