Perhaps he didn’t have any family of his own left in the world if that’s where he went after his mother died. I wonder where is the extended family or if any.
Another story said he was living in Palm Beach with somebody after his mother died, but he didn’t like it, so asked his friend if he could stay with his family. Most likely he wanted to get back close to the school to do the shooting. He does have a younger biological brother who was adopted into the same family with him.