I have only been watching days for a little over a year now, and i was wondering if some one could please tell me how brandon is nicole's brother? and also how he is related to abe, lexie and theo??? thnx!

Brandon and Nicole have the same mother who is Faye Walker.Brandon is Abe's son and Paul Mendez is Nicoles father...There for Brandon is Lexie's step son and Theo's half brother.

which is so sick cause brandon and lexie slept together

That's not really sick. Lexie's just a woman who's married to his father. Ain't nuthin new under the sun