Kay Panabaker (Jamie Bartlett) and Danielle Panabaker (Is) are sisters in real life. Born September 19, 1987, Danielle is the elder of the two. Kay was born May 2, 1990, and has quit acting way back in 2012 to work with animals and eventually became a zookeeper for Walt Disney parks.
The name of the recording star Jamie's mom is so smitten with, George Jackson, is obviously a composite of George Michael and Michael Jackson. They were both still alive back then.