HOW IS SHE 14
HOW IS HE SO CUTE
Genetic lottery, for the both of them, I suppose.
At least in the first case, pretty sure Anna has what one might refer to as 'tall genes' that probably helps explain why she's so massive for her culture and age, which also likely reflects in a very powerful metabolism to control her body fat, based on my own experience as a tall and thin person that doesn't need to do anything to maintain a slender, bony appearance virtually regardless of how much I eat.
To clarify, at this stage of the story, he hasn't been met but, uh...
Her father is a tall and large-built man, so I'm not surprised his daughter is also quite big, in nearly every sense. Seeing him in any of the anime scenes with Kyo was quite amusing, seeing the drastic difference in stature and build.