Like her sisters, Rosie had come to live in the Dumping Ground due to the fact that her mum had died. She then got fostered by Christie and Matt Perry along with her sisters. But Lily Kettle returns to the Dumping Ground. She is 6 years old.
Steve Kettle - Dad
Matt and Christie Perry - Foster Parents
Rosie is first known as Lily and Poppy's sister. She also later gets fostered, along with Poppy, and Lily temporarily.
We also see very little of Rosie in this series. She appears to prefer after a time with Matt and Christie, their stories instead of Lily's.