"We're not much alike, really. He was always dependable and practical...a complete bore, I'd say."— Lyndon on Edlin(src)
Edlin and Lyndon grew up as orphans in the slums of Kingsport. He taught Lyndon how to fight and use a crossbow, reasoning that it would give Lyndon time to run if things went awry. He became a member of the Kingsport City Guard and married Rea. She never told him of Lyndon's previous infatuation with her. She later gave birth to children.
Lyndon, who'd become a member of the Thieves Guild (against Edlin's advice) would tip him off to the Guild's hits while Edlin would bring the guards into the scene of the crime and play it off like a lucky catch. However, when Lyndon robbed the Merchants Guild's bank, Edlin showed up too early and was accused of being involved in the heist. Edlin was put in Kingsport's prison. Rea believed that Lyndon had been involved in Edlin's imprisonment, and convinced him of the same.
Edlin and a number of other prisoners were transferred from the Kingsport jail to the one in Westmarch, prior to the Reapers' attack on the city. Rea killed him in there. Lyndon later discovered his body, and the note Rea had left behind.