Lucas Lassiter is Connor's younger brother.
When their parents decided to have Connor unwound, they bought tickets to the Bahamas for the three of them. When Connor found out, he decided to go AWOL without saying goodbye to him. And, while Connor did consider saying goodbye to Lucas before he left, he was ultimately unable to.
It is unknown how much Lucas and Connor got along, but it is implied that while Connor cared for Lucas because they are brothers, the two weren't particularly close. Apparently, he and Connor used to fight all the time. Connor was constantly compared to Lucas in grades, sports - even though Connor was the one that taught him to play them all. While Connor was skilled enough to participate, he never had the dedication to stay with a team for a whole season. The more Lucas shone, the dimmer Connor's light seemed to their parents. It is possible that this is part of the reason Connor got into so much trouble and acted out. Connor has expressed resentment towards him for being "the golden child" their parents kept, stating that while Lucas "got the trophies", Connor got the detention slips. Connor later got over his resentment of Lucas by reminding him that it wasn't his fault what happened to him. He even begins to miss him very much.
While Connor was AWOL Lucas missed him a lot, too.
In UnDivided, his family, despite not knowing that Connor would be at the gathering, attended the All Saints' Uprising. Connor later arrived aboard an aircraft, and they all immediately made their way to Connor. Lucas called out to him and, despite his voice being deeper than when they last saw each other, Connor recognized it and spotted him in the crowd. The crowd attacked his parents, screaming out that they were 'unwinders' and should be unwound themselves. Lucas watched in horror and begged for Connor to stop them. When Connor came to them, he hugged his parents, and Lucas joined in.
- Lucas is among the characters Neal Shusterman named after a fan through a post on his Facebook page. He was named after Lucas Traub.