David's family?

Just watched this. There is a line where David tells the scientist character that he has no family. But there was an episode I saw on MeTV in which David visits his father and sister. It was one of the saddest episodes.

So does anybody know if something happened to the sister and father in a later episode? I haven't watched this show much since I was a kid. We could assume his father has died of old age. But the sister being dead would be unusual so you'd think David would volunteer some comment.

This movie had some extreme good and bad. Some great characterizations. The helpful scientist had such an original sort of personality. That bit that Yasmine does pretending to be a southern lady was hilarious. But visually the movie had a harsh sort of look. Shot on video I guess. And the background music ... yuck! Sounded like 70's porn or something! Smart story though, and Bixby was good as always.