Well, if you look for longer than a glance, there are a few differences between Florian and I that can tell us apart. I'm a bit taller than he is now, and he doesn't have any scars on his neck like I do.

[Which should be visible from the picture in the journal, since Ion doesn't cover them up anymore. It was just easier to have something distinct to tell them apart, especially given how much it seems to bother Florian when he's called by the wrong name.]

Oh, but you shouldn't have any trouble getting us confused with Sync. He usually wears a mask when he goes around the village, and he wears his hair differently as well.