I think I'm going to go with Elizabeth Heart. I like that.

And agreed. I think the two of them were probably closer to each other than their parents, though we can definitely work in some tragedy/awkwardness because, you know, parental abandonment. Aaaas for Robert's singleness. Heart would probably privately not see a big deal but she's so !into~! her job, the textbook says that it's a problematic symptom of his conditions. So she would be concerned from that angle and miss entirely the hypocrisy there.

EDIT: also the most unnecessary family tree