Hey OP,

I feel much the same about my father, he's very similar to yours and our backstories are pretty much identical.

He's became rather bitter since he became almost blind a few years ago and has now lung cancer since he heavily smoked since he was 14 or so.

He'll be 73 now, I don't think he'll recover.

Your post made me feel pretty bad about my behaviour towards him, although I visited him every second or third day when he was 30 km away in the hospital.

I guess your feelings will stay a while. Just be honest with them, and maybe talk with your mother about it.