How do we handle Dad accusing Mom of what she did in high school?

Thank you all for the replies....most of what you have answered with is in line with what we have been thinking is going on..Dementia.

Agree with Chicago Dad needs an evaluation it sounds as though he has or is developing some form of dementia. This must be very distressing to Mom especially as she is so dependent on him for her daily care. At the very least it is emotional abuse. do you think that now is the time when they should no longer be living alone. My read of this is that he is punishing your mother because she has become ill and can no longer take care of him and the house. I don;t think he is getting anything out of it just the satifaction of hurting someone who is too weak to fight back. He has become resentful of his new role. Over 60 years ago I doubt your mom was having much sex in high school.

Your father needs to be seen by his physician. That is not normal behavior and your mother should not have to endure it. In my mind, emotional abuse is just as bad as physical abuse. I am afraid he will start to accuse her of all kinds of things.

I too have to wonder why your father is feeling so insecure..Speak with him again and tell him how much it hurts your Mom..

If he doesn't behave this way in front of you did your mom tell you that he was going off on these tangents? Is she upset or does she not pay any attention to it?

If it's something your dad is doing when he and your mom are alone I don't know what you can do about it. You said you spoke to him about it and he shrugged it off. You can try talking to him about it again, maybe tell him that he is upsetting your mom and hurting her, maybe that will knock some sense into him.

Your profile says 'age related decline' but I have to wonder if there's some dementia going on with your dad. Or maybe, in being your mom's primary caregiver, he feels a profound loss of control and needling your mom about this petty and immature stuff makes him feel like he's more in control. But figuring out the why doesn't stop the behavior. I have to wonder how your mom reacts to his ranting? Does she get upset? Cry? Beg him to leave her alone? Your dad is getting something out of this I just can't figure out what it is. And three's not a lot you can do if this behavior happens while they're at home alone together.