One of the three 'slavery victims' is reportedly the daughter of a Second World War codebreaker, The Times (£) claims.
Josephine Herivel, in her fifties, is believed to be the daughter of John - a leading codebreaker at Bletchley Park who helped decipher the Enigma code.
She joined slavery suspect Aravindan Balakrishnan's extremist collective in the 1970s after moving to London to study, turning her back on her family.
When her father died in 2011 obituaries only made mention of two daughters, Mary and Susan, who now live in London.
Family friend Frances Presley told the newspaper: "They have tried to contact her for years. I know she was involved in some kind of cult group. My understanding is that she cut herself off [from the family]. I know they have always tried their best."
Aravindan and Chanda Balakrishnan were arrested on suspicion of slavery related offences amid claims that three women were held against their will for more than 30 years.