So based on this (only) image of the Hamada parents…
We know that Tadashi bares the most resemblance to his father
But which traits from which parent did Hiro inherit from?
Based on just looking at the parents, we already know that Hiro got the dark hair and his Asian traits from his father; but aside from that, there’s not much else to go on.
But then I noticed the eyes. Aside from the fact that they are obviously almond shape to correspond with his Japanese genes, take a look at the parents again. Tadashi’s eyes are slightly more narrowed, like his father, and the mother has very round eyes. Almost the exact same shape as HIRO’S.
Hiro has his mother’s eyes.
Also the mother looks to be a very tiny person - just like Hiro!
Oh and we can’t forget Aunt Cass, since she is their mother’s sister
Those smiles are uncanny to each other!
(it’s hard to see in the picture but the mother seems to be wearing a similar smile too)
So this means
that although it’s small, Hiro has inherited most of his features from his mother’s side!