He was born into the River family as seen since he was in Henry's will. Its assume that he changed his last name after Caleb was born and its been mention he been to jail. In "Dead to Me", Caleb thought the Jamie was his uncle but, he turns out to be Caleb's father.
Dead to Me
Jamie is helping Caleb and Hanna look through the stuff at Caleb's aunt's place despite that Caleb is not happy to be there and is being rude to him.
Jamie tells Hanna he hasn't heard from Caleb's father and that he wasn't much of a guy. He says Caleb's mother deserved better. He says Caleb's father left because he couldn't handle being a dad.
When Hanna and Caleb leave, Caleb's uncle takes her aside and gives her a baby picture of Caleb at six months. He asks her to hang on to the picture until Caleb's ready to see it.
What Becomes of the Broken-Hearted
it is discovered that Jamie is in fact Caleb's father, not his uncle. He meets Caleb and Hanna for coffee where Caleb decides to give him a chance. Ted gives him a job at the church, and Ashley invites Jamie and Caleb round for pizza and beer to celebrate. Jamie insists on paying for the pizza, and Hanna notices that he is holding a note that has the same mark on as the one she put in the donation box at the church. Is Jamie stealing from the church?.
I'm Your Puppet
Caleb and Hanna are together and happy, and Caleb is so glad Hanna got his father, Jamie, the job at the church. Hanna seems unenthusiastic and is still worrying about the church money she saw that Jamie had.
Caleb rants to Hanna about how his father is innocent about the church bell, and she reveals that she saw her money donation to the church in Jamie's wallet. Caleb is heartbroken, but believes her.
Jamie comes to Hanna's house, and is confronted by Caleb. Caleb yells at him, and Jamie seems confused, but leaves when Caleb tells him to. They cut off ties, and Caleb is hurt that his father betrayed him again.
Caleb and Hanna are talking at the carnival, and Caleb sadly tells her about how he'd hoped his father would be there for him this time. When Caleb goes to get them coffee, the church bell tolls, and Hanna gets an 'A' text revealing that Jamie was framed. Caleb comes up behind her and looks at her phone, reading the text.
A is for A-L-I-V-E
Hanna mentions Caleb is still searching for Jamie.
Upon Caleb's return in he has reconnected with Jamie off-screen. Jamie had been out on a boat fishing every day. Caleb told him how the foundry made the mistake that mixed up the church bell and Jamie wanted to know if that was the only reason he was there. When Caleb explained that he's sorry for not standing up for him, Jamie handed over his line of fish. The two scaled, cleaned and cooked the fish as they made amends.