The family of Shamima Begum have written to Home Secretary Sajid Javid to ask for help in bringing her newborn son to Britain.
The letter, penned by the IS teen's sister, Renu Begum, says the baby is a "true innocent" who should not "lose the privilege of being raised in the safety of this country".
"We are sickened by the comments she has made, but, as a family man yourself, we hope you will understand that we, as her family cannot simply abandon her," Ms Begum wrote.
- Read more: Shamima Begum: 288,100 votes cast in talkRADIO poll
- Read more: Jeremy Corbyn: Shamima Begum has a right to return
"We have a duty to her, and a duty to hope that as she was groomed into what she has become, she can equally be helped back into the sister I knew, and daughter my parents bore."
The family said they have had no contact with Ms Begum and had only learned she had given birth to a boy through media reports.
'Shocked and appalled'
Shamima Begum being interviewed in a Syrian refugee camp. Image: ITV News
They made clear that they were "shocked and appalled" at the "vile comments" Ms Begum had recently made to the media.
Ms Begum was one of three schoolgirls to leave Bethnal Green to join the terror cult in 2015 and resurfaced heavily pregnant at a Syrian refugee camp last week.
"That year  we lost Shamima to a murderous and misogynistic cult," her sister wrote.
"My sister has been in their thrall now for four years, and it is clear to me that her exploitation at their hands has fundamentally damaged her."