Jonas Richard Corbin:
-Born in Foxwood, New Hampshire to Richard and Donna Corbin on August 22, 15 years before the events of the series.
-Jonas lived across the street from the wealthy Bernhardt family, and became good friends with their daughter Kiera, who was just a month and 10 days older than him. Their son Adrian also became somewhat of a big-brother figure to Jonas.
-When he was three, Jonas taught himself to read.
-Shortly after Jonas' eighth birthday and before he started third grade, he and Kiera were climbing trees, and Jonas dared Kiera to climb to a particular branch. The branch broke, and Kiera fell and broke her left arm. Adrian, who was in charge at the time, lashed out at Jonas physically and verbally in a combination of anger and fear. This is why Jonas is afraid of Adrian. As a side note, although Adrian and Kiera have both forgiven Jonas for the accident, he hasn't forgiven himself, which is part of why he's so FINE* (in the Aerosmith sense).
-Shortly afterwards, Jonas' parents' divorce was finalized, and he and his mother moved to the other side of town. This meant that he and Adrian would not have a chance to reconcile, nor would he see Kiera recover. To make matters worse, Jonas and Kiera were placed in dfferent classes until seventh grade, and so they grew apart, especially since the Corbins' custody agreement allowed Jonas to only see his father every other weekend, which was also his only opportunity to see the Bernhardt siblings. He was able to sign Kiera's cast, though.
-In an interesting coincidence, though, the house that Donna and Jonas moved to was next door to Kiera's best friend Chloe Seaver and her brothers Mark and Justin. Jonas quickly befriended Chloe, and Mark became a new big-brother figure to him, despite being a bit of a bully.
-When Jonas was in third grade, the Bernhardts' cat Angel had kittens, and they gave one of them to Jonas, who named him Leo after the constellation because he was going through a space phase at the time.
-Despite the divorce being relatively amicable, Jonas still felt lost and insecure, which led him to adopt his class-clown persona. Since it made him popular, he kept it up even after things stabilized.
-When Jonas was in fourth grade, he met Brad Thompson, and they became best friends, often having play dates at each other's homes. Brad also befriended Chloe, and the pair became a trio. Jonas also met Brad's sister Mia at this time, but never really knew her well, despite her being only one year his junior.
-Sometime around this time, Jonas' father Richard started dating a woman named Monica, who he eventually married, making her Jonas' stepmother.
-A year later, when Jonas was in fifth grade, Monica gave birth to his half-sister Samantha, with whom Jonas has always had a complicated relationship - he loves her, but at the same time resents her for stealing his father's affection.
-In seventh grade, Jonas and Kiera were placed in the same section, and Jonas officially started crushing on her.
-When Jonas was thirteen, Samantha stabbed him in the arm with a fork. To this day, he refuses to sit next to her at meals requiring forks.
-The series starts with Jonas as a high school sophomore who's had the good fortune to be assigned the locker next to Kiera's in the same year that Adrian went off to college.
*Bleeped-up, insecure, neurotic, and emotional.