Esther and Judas knew each other as kids and became friends through Widogast. Esther assumed that Judas and his family had moved away at the start of highschool. In truth, Judas never left.
Judas and Widogast were once childhood friends, but they haven't officially seen each other since highschool. Judas has been keeping a close eye on them, though. Some crushes never really go away.