Glee mix up
Imagine that Blaine is Sebastian, Marley, Kitty, & Quinn's brother. Burt and Kurt are Finn and Carole's step family. Mercedes and Unique are siblings. Rachel is Will and Emma's daughter. Santana is Beiste's daughter and Lauren's sister. Britney is Sue's daughter. Sam is April's son. Hunter is Cassandra's son. Jake and Puck are Shelby's sons. Ryder is Holly's son.
(I know this will never happen except for the Hudson-Hummel's)