Before Andrew was born he allready had done something very special. When his father died in an attack of the Millers he brought him back to life. Using his special power. He was born just a few weeks after that. His older sister is really proud to be a big sister and is very caring for her little brother.
A few months after his birth his first cousins are born. He is very interested in the twins and wants to know all about babies. When he grows up he gets a second sister. Which makes his family complete. His favourite toys have all to do with pirates and all he can think about is the braveness of his heroes. His parents give him a pirate room. Being the only boy he sometimes struggles to find someone to play with. Most of the times he plays with his father or with his cousin, Damien Saphire.
When he is two years old, he gets kidnapped by May Miller, who wants to take revenge on his parents. AJ is able to get away originally, but he gets found behind the garden shed and is taken anyways. Eventually he gets freed, and he makes a swift recovery from the traumatic experience, returning to being the joyfull kid he was once before.
Soccer remains one of his other favourite things to do. His uncle Seth is the one playing that game with him most of the time.
At Highschool he is in the same class as his twin cousins, Amanda and Alexis. He is a sophomore and makes friends quite quickly. He is pretty atletic and joins the soccerteam.Soon he develops a liking towards Ivy Woods. Ivy goes along with it to keep her cover. Tom Wayland isn't pleased with this, and he poses as a player from the other soccerteam to make this clear to AJ. He gets beat up at the parking lot by some people because he allegedly was to blame for the team's loss that evening. There he accidently uses his powers to break a lantern, and following that he doesn't defend himself at all, in fear of hurting someone. During spring break he spends a lot of time in Divitia, getting control over his powers.
When he returns after spring break, he is all energised. With an adapted schedule for magic and atheltic training (by Phoebe and Justin), he gets himself in check again. He is able to bring his team to victory every single game for the rest of the season. This earns him the spot of team captain in his Junior Year. He soon gets a relationships with Valentina, an ambitious cheerleader. He admits to his best friend he originally only does this to tease his sister, who is not great friends with her. Eventually he develops feelings for the girl. This results in heartbreak, when Valentina reveals she was also using him to get to his friend. When she turns out to have cheated on him, they break up. AJ swears off girls in his senior year, and continues going through highschool as a single man, occasionally having flirts. He does re-establish a connection with Ivy, after he uncovers her nature. He helps her with juggling school and vampirism, aiding her with blood he gets from his family. He graduates second in his class, and gets a scolarship offered. However when he finds out the scolarship is between him and another teammate, he passes down the chance, because he isn't certain of what he wants to do in his life.
That summmer he works at Decade, with his father, while he comes up with a plan for the rest of his life. He decides he doesn't want to do anything magicrelated like his family. When Amanda goes to Europe to figure out what she wants, he decides to join her. They travel some places and he has some one night stands in every city they go to. He uses his bartender skills to finance some of their expenses.
When he gets to London he meets Nathalie, a girl of his age. AJ and Amanda then continue their trip but when they are on their way back home AJ changes his mind and he books a flight back to London. He keeps his promise that he will see Nathalie again and shows up on her doorstep one month after they first met. They fall in love as he spends the fall in London. When he returns home at Thanksgiving he brings Nathalie, and he declares to his cousins and his sisters that he has dropped his bachelorstatus.
Andrew's past with Ivy gets adressed again when he meets Aria officially at the motel, as their first meeting took place while Aria covered for Ivy. AJ is anything but pleased about the fact that Aria and Matt basically run the Millers, but he is reassured by his father that the Millers are in good hands. Nathalie gets assigned the former room of Emilia Brown and AJ declines his own room when Matt offers it to him. Andrew gets involved into Antoine's task, hunting, and he also bonds with Scott over their pasion for Soccer.
Towards the end of the season, Amanda mentions that AJ is barely at the Silverstone house, to which he replies that he and Nathalie are going to find their own place to live. He asks the necessary permission to his aunt Alyssa, before signing a lease on an appartment down in Water Street. His envolvement in the Millers increases, and AJ finds himself in the magical world, something he had told himself he wouldn't do. When he mentions it to Aaden, his cousin tells him about the conversation he overheared between his parents. Andrew goes to investigate and he finds out there are troubles at the Silverstone company. He volunteers to move to LA to keep an eye on things, granted he can live there instead of Waterfall Creek (which is what he originally promised his parents.) When they reluctantly agree, AJ and Nathalie move to LA. At the end of the season, they are spotted at an adoption agency.
He is a bit resentfull of his magical powers and his vampirism. AJ is kind hearted, and values honesty. He is very active, and as a kid he was very playfull. As a teenager, he often experienced trouble concentrating, this improved when he got a better grip on his life and his body.