Mizel Pomdak
Born as an average human to an average human family on an average planet in the Mid Rim, Mizel Pomdak could have easily been an Imperial loyalist. His parents were; while they didn't work for the Empire, they happily ate up the propaganda coming across the networks. But Mizel? Mizel knew better.
He was only a kid, but he could already tell when the Empire was lying. He just didn't know what to do about it. That was, until a brave young boy the same age as him sent out a message— stand up and fight. If this boy could fight for a better galaxy, he could too. Mizel ran away from home and sought out the Rebellion; he wanted to do his part, too.
As it turns out, war was a lot different than he was expecting. Less heroic stands against the enemy, a lot more equipment checks and ship repair. But Mizel did his duty, and learned to fight as he went. All the while, he tried to shut out the part of him wondering what he was even doing here, trying to fight in a war he had no place in.
Notes:
In his primary verse, Mizel is a teenager. That said, for timeline reference he is roughly the same age as Ezra and Luke.
My main canon has Mizel remain with the Phoenix group under Commander Sato (and later General Syndulla), rather than going to Kinrah with Commander Ryden.
Since the actual canon we know about Mizel is very small, 95% of his canon is my own concoction.