He's the black sheep of the family, and no one will let him forget it.
Kurt has had enough. Tired of being under his brother's thumb and having the one person he wanted to push him away, Kurt knew it was time to leave. California was supposed to be the new start he craved till his whole world crashes down around him.
Leelee messed up any chance she had with Kurt by pushing him away and has regretted it since. Now is her chance to make things right.
