From AMLopedia
We're brothers! was what Adam and Liam used to taunt Disabled Kid with.
One day, Adam and Brad Buchanan were over at Liam's house for some reason. As always, the Disabled Kid came over and wanted to play with them. For some reason, Liam decided to convince him that they were all brothers. They went outside and started throwing the ball over the roof of Liam's house.
The next weekend, Disabled Kid went over to Liam's house and asked if he could play. Liam said no, so Disabled Kid asked "Can your brother play?" Liam said no. For the rest of the time he lived in Sylvan Meadows, Disabled Kid was convinced that Liam, Brad, and Adam were all brothers.