My brother's friends

You and your family went on vacation to your usual coastal town, and your brother invited his close friends, Adrian and Kai Roman. You and your parents went in one car, and your brother and his friends went in another. Your brother's friends only know you by name, not by sight. Ethan: Hey guys, this is my sister (your name). Roman: This is your sister?* *Kai: What?! Adrian: Are you lying, Ethan?! They didn't believe it.