Didn't he adopt her and raise her after his parents both died? I think he was in his early 20's and she was like a young teen.
I don't know the guy, nor am I defending him, but that seems like a pretty stand up thing to do.
(Just thought I'd post something up here that wasn't bashing a dead guy.)
Yes, he did adopt her. The following article from The Guardian fills in a lot of her background info.
Darline Graham Nordone: Lindsey Graham’s sister and interim US senator | US politics | The Guardian
https://share.google/EjgSOQuMeuT6RAhac