The baby of Shamima Begum, a British-born teenager who fled London to join the IS, has died in Syria.
The death has been confirmed by the US-backed Syrian Democratic Forces, who declined to specify how or when it happened.
According to the medical certificates obtained by the BBC, the three-week-old boy died of pneumonia.
Shamima, who was stripped of her UK citizenship despite her wish to return, had previously lost two other children, apparently from illness and malnutrition.

US, Iran weigh peace plan as Trump's warning nears deadline
Intelligence head of Iran's Revolutionary Guards killed in strike, media say
Six injured after Iranian attack on residential area in Kuwait
Russian drone attack on Ukraine's Odesa kills three
US snatches airman from Iran as Trump, Israel ratchet up pressure