Evan is the older brother of Armin and Alexy. They share biological parents, both of whom are deceased. He attended military school, where he met and befriended Kentin. His age is unknown, but it's clear by his age and appearance that he is a grown adult, and he frequents bars and clubs without any trouble. He entered military school at age 10, and suffered a lot of bullying. As a child was followed by two men and was violently assaulted, and he was forced to fight back.
He is seen to be a flirt in Episode 37, when he shows an interest in Rosa at the mall, however he does not seem to respect her boundaries. He's also antagonistic, getting into fights and teasing people he encounters at Moondance club. In Episode 38, this antagonising attitude gets him into trouble, leaving him with bruises and broken ribs after criticising the appearance of two men he encounters.
Kentin is good friends with Evan from military school, and says that Evan taught him to be confident. He looks up to, and is influenced by Evan. However he influences in a negative way, and Evan doesn't realize how weird his standards are in a non-military environment.
Armin was also pleased to meet Evan, but was not as excited to have a new brother as Alexy was. Though, like Alexy, he grew uncomfortable with Evan's attitude following their trip to the club. However, they have a real talk and patch things up in Episode 38.