Brian Seabury (b. 1995) is the son of Jane and Kenneth Seabury, the older brother of Bonnie Seabury, and a resident of Old Larkin in Larkin Mills.

Brian became friends with Alexandra Quick when she and her mother moved from Chicago to Sweetmaple Avenue in Old Larkin. After Alex jumped from the roof of her house in 2002 on a dare, landing lightly without injury, she attempted the same feat again with Brian; they both wound up in the hospital, she with a sprained ankle and he with a broken elbow and concussion.

During the summer of 2007, he and his sister accompanied Alex to Old Larkin Pond, where Alex believed a naiad lived, but left Alex at the Pond to get Bonnie home before dark. Two days later, Brian got a visit from Alex, who convinced him to return to Old Larkin Pond and help her search for her bracelet, which she had dropped there. Brian and his sister snuck out and met Alex at a nearby park, witnessing her altercation with Billy Boggleston and his friends. They made their way to the Pond, where Bonnie spotted the bracelet at the edge of the Pond before a kappa tried to pull her into the water.

Brian and Alex incapacitated the kappa, pulled Bonnie to safety, and retrieved Alex's bracelet, but the Seabury's furiously returned home without speaking to Alex. Alex later broke her grounding and meet him and explain her scholarship to Charmbridge Academy, but he denied the existence of magic despite his experiences with her. A week later, on the first day of school, Brian waited with Bonnie and Billy for the bus to Larkin Mills Elementary School, and ignored Alex when he saw her waiting for the Charmbridge Academy Bus.

Brian saw Alex again on Christmas Eve while ice-skating at Larkin Mills Pond. His sister approached Alex first, but he dragged her away after Billy Boggleston mocked her for going to a "special" school and Brian called her a freak.

In July of 2009, Brian encountered Alex when she walked Bonnie back to Sweetmaple Avenue from Old Larkin Pond. He explained to her that Bonnie had been getting into trouble more often, and that Mrs. Seabury considered Alex a bad influence on Bonnie.

During the summer of 2010, Brian intervened during a fight between Alex and Boggleston at the Sweetmaple park, and later followed Alex to the Old Larkin Pond where he encountered Diana Grimm. In December of that year, he approached Alex while she was home on Winter vacation and apologized for his treatment of her, admitting that he wanted to be friends with her again; she told him that she would "think about it."