Ingen av dem undertryckte sin magiska kraft
Newt är helt klart om detta i manuset; en Obscurus utvecklas bara när magi är avsiktligt undertryckt:
Newt: Before wizards went underground, when we were still being hunted by Muggles, young wizards and witches sometimes tried to suppress their magic to avoid persecution. Instead of learning to harness or to control their powers, they developed what was called an Obscurus.
Fantastic Beasts and Where to Find Them (2016)
De tidiga kapitlen av Filosofens sten ger oss en inblick i Harrys före Hogwarts barndom, och det är uppenbart att han hade incidenter av oavsiktlig magi redan innan han blev elva:
Once, Aunt Petunia, tired of Harry coming back from the barbers looking as though he hadn't been at all, had taken a pair of kitchen scissors and cut his hair so short he was almost bald except for his bangs, which she left "to hide that horrible scar." Dudley had laughed himself silly at Harry, who spent a sleepless night imagining school the next day, where he was already laughed at for his baggy clothes and taped glasses. Next morning, however, he had gotten up to find his hair exactly as it had been before Aunt Petunia had sheared it off He had been given a week in his cupboard for this, even though he had tried to explain that he couldn't explain how it had grown back so quickly.
Another time, Aunt Petunia had been trying to force him into a revolting old sweater of Dudley's (brown with orange puff balls) -- The harder she tried to pull it over his head, the smaller it seemed to become, until finally it might have fitted a hand puppet, but certainly wouldn't fit Harry. Aunt Petunia had decided it must have shrunk in the wash and, to his great relief, Harry wasn't punished.
On the other hand, he'd gotten into terrible trouble for being found on the roof of the school kitchens. Dudley's gang had been chasing him as usual when, as much to Harry's surprise as anyone else's, there he was sitting on the chimney.
Harry Potter and the Philosopher's Stone Chapter 2: "The Vanishing Glass"
Även om vi inte vet mycket om Hermions barndom, hade hon förmodligen liknande erfarenheter (men utan det flagranta barnmisshandeln borde jag tänka).
Det är intressant att Harry verkar vara den perfekta kandidaten för att bli en Obscurus; Eftersom han var helt bokstavligt missbrukad för sina magiska utbrott, verkar det logiskt att han skulle försökt för att undertrycka dem. Även om jag inte har några bevis för detta, misstänker jag att hans magiska okunnighet faktiskt är vad som skyddar honom; eftersom han inte hade någon uppfattning om vad som orsakade hans utbrott, visste han inte hur att undertrycka dem.
Men oavsett hur det är klart, så misslyckades han med att undertrycka sina magiska krafter. därmed ingen Obscurus.