Seems like Mr. Terrific's son is the last member
Yeah, thinking about Wolfman/Perez's Titans I'd argue that one of the themes of the run, if not really the main theme, is pretty heavy daddy issues:
Dick: His father is Batman
Donna: Her parents died at the age of 2
Starfire: Sold her to slavery
Beast Boy: His father is Mento
Cyborg: His father is responsible for his accident
Raven: Self-explanatory
Jericho: His father is Deathstroke
Terra: Illegitimate daughter of a king
I used NTT as my example but I could have used easily Runaways instead. Rebelling against your parental figures, as freudian as it sounds, always seems to be a major theme in these runs and it seems to be forgotten here.