Reema Iqbal, 30, and her sister Zara, 28, left east London for Syria in 2013, and between them now have five boys under the age of eight.
London: Britain has revoked citizenship from two more women who joined the ISIS group in Syria, a newspaper reported Sunday, raising questions about the fate of their children.
The revelation follows a row over a similar decision regarding London teenager Shamima Begum, whose newborn baby died in a Syrian refugee camp last week.
Reema Iqbal, 30, and her sister Zara, 28, left east London for Syria in 2013, and between them now have five boys under the age of eight, The Sunday Times newspaper said.
Citing legal sources, the paper said they had been stripped of their British citizenship.
The pair, who are of Pakistani heritage, reportedly married into a terror cell linked to the murder of western hostages.
The British interior ministry said it does not comment on individual cases.
A spokesman said: "Any decisions to deprive individuals of their citizenship are based on all available evidence and not taken lightly."
Begum, who married a Dutch IS fighter, was located by journalists in a refugee camp after fleeing fighting between the terror group and US-backed forces.
She had asked to return to Britain with her baby, after her two other children died under ISIS rule.
Interior minister Sajid Javid revoked her citizenship amid security fears, but has been criticised for not doing more to help her son.
British law states that the government cannot remove a person's citizenship if that would make them stateless.
Begum was thought to be eligible for Bangladeshi citizenship through her parents, but Dhaka said she could not go there.
Javid has previously said that more than 100 individuals had already been deprived of their British citizenship.