OK, I looked at the sims, and it's definitely a replacement.
Sim1 YA (3 days in): Excitable, Eccentric, Brave, Dramatic, Dislikes Children, Bookworm (S)
That's the right number of traits, and she got "Dramatic" on aging up. I would probably have to look at an old save what was replaced by "Dislikes Children"
Sim 2 Teen (11 days to transition): Unlucky, Excitable, Evil, Ambitious, Loves the Outdoors
Should have a social trait instead of a fifth base trait. Not sure which trait got replaced, either.
Sim 3 Teen (11 days to transition): Slob, Excitable, Ambitious, Dramatic, Genius (S)
Right number of traits, and Slob replaced something.
Alternatively, the sims all lost a trait during some game glitch, as the fourth sim in that age range had a similar issue last time. It's also weird that it's all the same family. I guess I should leave it at that and hope it doesn't repeat. MC to the rescue.
Sim 2 had all of his traits except one replaced at some point in the past.