Oh great points! I never thoughts about the fact that Ahura and Luna are really the only Inhuman kids that have been looked at in detail, and Luna isn't even a full Inhuman. Treste and Irelle do support that idea though. We really do have no idea what the typical Inhuman aging cycle looks like. The only thing that's weird about that is that Ahura is calling himself 16 (?) when he wouldn't be 16 by actual years, but by physical age... Unless Inhumans age quickly as kids and then start aging slower as they reach their teen/adult years? Well now I'm confusing myself lol
the fact that Luna Maximoff was literally born before Billy and Tommy but bc of the retro-reincarnation* the twins are full grown adults and Luna is still a middle-schooler.
*nobody in the mid-2000s was playing close enough attention to the timeline, also because Luna is the Franklin Richards of Atillan and will never age.