On one hand, there is an official piece of merchandise that lists Atom's age as being 10 years old:
On the other hand, they also list Cobalt as being Atom's younger brother on this merchandise, which I'm 99% sure is a mistake. I've never seen any of the 1960s episodes with Cobalt, so I can't confirm or deny whether Cobalt is technically supposed to be Atom's older brother (according to the Astro Boy wiki, the anime says that he was created before Atom as a prototype, while the manga says that he was created as a copy of Atom).
I've always assumed that Atom is created to look 9 years old because of Tobio being 9 when he died, but honestly, the 10 year old claim sounds plausible as well in my mind.
Uran and Cobalt are never given a specific age that they're supposed to look like (as far as I know), but I think I've assumed that Uran is supposed to look 7 or 8 years old, and Cobalt is supposed to look 11 or 12 years old.
Regardless, it seems correct in my mind to put about 2 years between each sibling. So, either, it could be...
- Uran = 7
- Atom = 9
- Cobalt = 11
- Uran = 8
- Atom = 10
- Cobalt = 12
I like #1 a little more, but #2 is also plausible in my opinion.
Anyway, I'd like to know if there's any official source that states how old Atom and his siblings are supposed to look (beyond Tobio being stated to be 9 years old).
Otherwise, I'd like to know if anyone else has thought about how old Atom, Uran, and Cobalt are supposed to look, and if you have, how old do you think they look?
Also, if you're wondering, I left out Chi-tan because I think it's assumed that he's supposed to look less than 2 years old.