Why Keith is actually 16+ in the S6 flashbacks and why he’s so small:
Okay, so lets start with this screenshot:
THIS IS NOT AT THE GARRISON. Look at the teacher, she’s in plain clothes, so are the students. This is a high school and Shiro is here to recruit students. Assuming the Garrison works like a Service Academy, it’s like a college and requires a high school diploma. The minimum age for service academies and ROTC programs is 17, and it’s safe to assume that that is the Garrison’s minimum age requirement too. I guess they might make exceptions for extraordinary students, but I honestly doubt it.
This next scene is also not at the garrison, and occurs shortly after the classroom scene:
Now, we know that is Keith’s bike. We also know he and that he can probably fly it at this point. Why does that imply he is at least 16? Because he lives in a group home, and any younger than that and there’s no way he would have a chance to get away and learn. At 16 he could get a license, which his caretakers couldn’t stop him from. Even with a license I doubt he has insurance though, meaning he can’t fly the thing in public.
My personal headcanon is that one of the workers at the home knew about his passion for flying and turned a blind eye when he snuck out to the desert to practice. This person is the same one who points Shiro in his direction, where he sees Keith fly for the first time and convinces him to join the garrison.
It’s this last scene that really has me convinced Keith is in his mid to late teens though:
Here, when he’s sitting outside the teacher’s office with the other kid he presumably got in a fight with. The other kid is obviously an older teenager, and is Keith’s classmate, meaning they if they aren’t the same age they must be at least close to it.
How do we know? Look at the gold stripes on their shoulders. The strips mark rank, and presumably how long they’ve been there. They each have one stripe on each shoulder, marking them as younger students. Older students have two stripes. In the first episode the garrison trio all have two stripes on each shoulder, and so does Matt at the launch in Pidge’s flashback.
The stripes are also used for officers. Look at Shiro, in this scene he only has two, and the officer he’s defending Keith to has three, it’s his superior. At some point Shiro gets promoted because in the picture from the Kerberos news report he has three.
Anyway, back to the point. In this scene Keith also talks about going back to the home. Home refers to a group home for children in foster care. Generally teens that get placed here, usually due to a lack of foster parents or because of behavioral issues, though there can be other factors. I’m not going to go into all that in this post, just wanted to note that these homes tend to house older kids because they are harder to place than younger ones.
So that’s why I believe Keith is 16+, but why is he so gosh darned tiny?
There are a few potential explanations for this:
Keith could just be a late bloomer, potentially due to his Galran heritage. We haven’t been given a lifespan for the Galra, so if they live longer and age slower they probably grow slower too. I mean, Krolia looks the same in the flashbacks as she does now, and 20 years have passed.
Keith’s growth could be stunted due to lack of food. He was a foster kid, and it is quite possible he just didn’t get enough to eat, either because there wasn’t enough to go around, or because food was used against him as a punishment. One or two bad experiences could have left him scared to ask for more or take seconds even when offered.
He’s also half Galra. The Galra are also more muscled and most look like they have a very low body fat percentage. Muscle tissue burns two to three times as many calories as fat, meaning Galra need to eat a lot to maintain their weight, and kite need to eat even more, because they aren’t just sustaining what they have they’re adding to it. There’s also the possibility he needed vitamins and minerals to grow that couldn’t be found on earth. His caretakers may have unintentionally been underfeeding him because they were treating him like a human, not a Galra
So yeah, pre-Garrison Keith was tiny, but he didn’t stay that way:
