Wait. I thought he was her cousin??

Nope, the white haired guy is her cousin's cousin he is from perdels side of the family while Ria is from Silvia's side of the family. Ahin is the first cousin of the blue haired dude while Ria is the second cousin of the blue haired dude. But Ahin and Rian aren't related to each other (thankfully) though it must be fun for the blue haired dude to have cousins from both side of the family having a thing for each other