S4, E18: As Lily awaits the consequences of her decision, William van der Woodsen (recurring guest star BILLY BALDWIN), CeCe (recurring guest star CAROLINE LAGERFELT) and Lily's sister, Carol (recurring guest star SHEILA KELLEY – Sisters, L.A. Law, Lost, Matchstick Men), come into town to support her and be part of a Taschen photo shoot on "modern royalty" in which the Rhodes family is participating. Unbeknownst to Carol, who has always chosen to keep her daughter, Charlie (recurring guest star KAYLEE DeFER – Flicka, The War at Home), far away from the Upper East Side, Charlie has followed her to New York to meet Serena and the rest of the family. Meanwhile, Blair has an epiphany about her future, and grapples with the knowledge of whom she's destined to be with.