My thought would be closer to "He might want to talk about it, but if he says something like 'that's me and Jan. We were only married a little while, and I haven't thought about her in years,' don't push."
If the LW's father said something like that, it might be the truth: a brief marriage decades ago, with no children, might not have been important in the story of his life. Or he might not want to talk about it for some other reason. But "he doesn't have to answer" doesn't imply "you shouldn't ask, in case he doesn't want to answer."
no subject
My thought would be closer to "He might want to talk about it, but if he says something like 'that's me and Jan. We were only married a little while, and I haven't thought about her in years,' don't push."
If the LW's father said something like that, it might be the truth: a brief marriage decades ago, with no children, might not have been important in the story of his life. Or he might not want to talk about it for some other reason. But "he doesn't have to answer" doesn't imply "you shouldn't ask, in case he doesn't want to answer."