What if the reason that Keith is so small (by galra standards) is that he’s malnourished (by galra standards)?
When I look at the galra, I see “obligate carnivore”. Fangs, claws, glowy eyes? Yeah, that reads “predator” to me.
Now, Keith is only part-galra (we don’t know how much), but what if he inherited some of their nutritional requirements? His dad is implied to have known about Keith’s heritage, so he probably knew to let his kid eat as much meat as his growing body could pack away, but what about after Keith was orphaned? If he was in the foster system, how often would Keith have had meals that even included meat?