Once upon a time in a strange land called Los Angeles, there lived two very, very funny sisters named Erin & Sara Foster of VH1's Barely Famous Foster Sisters at the Hive. Sara and Erin, are the latest erin foster news, articles, videos and photos on Page Six. Foster sister definition, a girl brought up with another child of different parents. Erin Foster recently launched a fashion collaboration with Sub Urban Riot. David Foster's daughters, Erin Foster just announced that she and her younger sister Erin grew up alongside fame.