I, too, don't like to speculate much on his family life (anymore).
Old habits die hard, and I sincerely believe that Stevie and Lindsey are simply so comfortable with one another at this point. It's easy to understand why one would seek comfort in the form of a hand squeeze or hug when performing for the masses. Or even get a bit lost in the moment. "Ten thousand voices cryin' 'on with the show.'"
But I sometimes find it a bit odd. That a couple that broke up in the 70s would continue to go back and forth to this day. I was a bit taken aback when Lindsey "admitted" that "It Takes Time" was inspired by Stevie. I don't think it truly ended in the 70s and there is a lot we don't know. As long as they continue to talk about their relationship, people will stay interested in it. There is a strange fascination there.
Also, I think Kristen is a very secure woman and I give her props for that. You'd have to be!