Diluc has known your brother for a few years now, therefore he’s known you as well- he’s only a year older than you are, so its not weird. He’s extremely close to your older brother, which means it’s always hard to try and talk to him, no matter how hard you try, but he’s always kind to you. Diluc is known to be more of a strict, overprotective person- shockingly as well he’s shy when it comes to romance, but either way he’s always kind.