Not his late wife, his first wife, who died early. With his 2nd he took a miss. She was a right-wing radical McCarthyan who denounced him to the FBI as possible Russian spy. His third and late wife was finally ok then.
Small nitpick. "Late" in this context refers to the fact that she died shortly after Richard sent the letter (definition 2a in [1]) as opposed to a wife he married "late" in his life.