2 Works in Buffy/Lost Boys
Several years after the events of the movie Lost Boys, Michael Emerson finds himself in need of a vampire expert. His search leads him to Sunnydale, to consult with Rupert Giles.
Begins long before Lost Boys the movie, and before the BtVS series began.
Even with the same upbringing, brothers can take different paths to reach their goals. Just look at Richard and Max Wilkins for example...