Casey was adopted by Sam from China. Sam may have adopted her sometime after filing for divorce from Ginny seven years prior. It is implied that Sam's conservative mother Marilyn is having difficulty treating Casey as a "real" granddaughter, that she often makes remarks about her Asian roots. Sam mentions Marilyn bowing to Casey at Thanksgiving.
During the eighth season, Casey attends a Christmas dinner at the Truman home in Connecticut. After her grandfather George dies, Grace accidentally scares Casey by telling her about her his ghost following her around.