Question: Sapphire Battersea is the 2011 sequel to "Hetty Feather", written by best selling English author Jacqueline Wilson, whose  children's novels frequently feature themes of adoption, divorce and  what type of illness?
Sentence (from "Hetty Feather (TV series)"): Series 3 started airing on 8 May 2017 and finished airing on 10 July 2017.
Relevant evidence: No