Fatoumatta Hydara, 28, died along with Fatimah and Naeemah Drammeh, aged three and one, after their home in Fairisle Close, Clifton, was set alight in November last year.
Jamie Barrow, 31, had admitted their manslaughter but denied murder, insisting he assumed the property was empty when he poured petrol through the letter box and started the blaze.