Carole and Burt get married and Sebastian and Kurt become stepbrothers (Carole is Sebastian’s mom). At first Sebastian hits on Kurt because he knows it annoys him and that’s the kind of person he is but eventually he begins to have real feelings for him…

Sebastian: Let’s get a few things straight. Kurt’s too good for you, New Directions is a joke and one of us has a hard luck case of the gay face, and it ain’t me.
Blaine: Why are you so angry?