Hau and Gladio barely look different at all. I guess they're already pretty baby-faced.
Hau received a little blush, some tweaking to the eyelashes, and slightly wider eyes... And appears to be the more busty of the three. Only difference I see for Gladio's face though is "her" eyelashes. My guess is that is deliberate to keep that slightly older "bad girl/tomboy" vibe going.
