They were also mentioned in The Summer Before, after Stacey McGill and her parents had just arrived at their new house. They had many visitors, and it is said that Stacey's favourite visitors were the Hansons, who supplied them with takeout menus.
The Hansons are probably a family (with a big backyard) in the neighborhood.
They are probably friends of the Thomases, considering Sam and Charlie are allowed to go in their backyard (without permission, it would be considered tresspassing) and play football.
They probably live somewhere on Bradford Court , the street Kristy and Mary Anne lived on at the time (along with Claudia Kishi, who, unlike Mary Anne and Kristy, didn't move) or two blocks away on Faucett Avenue, the street where Stacey McGill had her first house in Stoneybrook (that Jessi Ramsey later moved into).
They could also be friends of Charlie and Sam's from Stoneybrook High School (SHS).
It has never been confirmed who they are, where they live, or anything besides the information on this page.