Sobieski's first name, "Liliane", was the name of her paternal grandmother. One of her middle names, "Elsveta", is derived from "Elżbieta", which is the Polish equivalent of "Elisabeth". Her maternal grandfather, United States Navy Captain Robert Salomon, was Jewish. Her maternal grandmother was of Ashkenazi Jewish and Dutch descent. Sobieski grew up in a "pan-religious" family; she has said that she is "proud of [her] melting pot roots". She graduated from Trevor Day School in 2001 and studied literature and fine art at Brown University but did not graduate.