The former London Mayor - who has five children altogether - revealed in his memoir, 'You Can't Say That' that he had two girls and a son with journalist, Philippa Need and activist, Janet Woolf. He was living with his then partner, Kate Allen at the time of the babies' conception.
According to the Mirror, Mr Livingstone, 66, hints in the book that he may not have used artificial insemination, possibly suggesting he slept with the women whilst still in his relationship with Kate.
He wrote: "I had never been romantically involved with Miss Need but I knew she would be a great mum so I offered. We agreed I'd help but not live with them."
Philippa Need, who later had a child of her own, said she was neither "surprised nor angry" about Ken's revelations.
Do you think it is irresponsible to father children with someone you have no intention of being in a relationship with, or do you think Ken was generous to have 'donated' his sperm?