“You get excited if you’re pregnant. You go to the doctor’s appointment and they say you have two babies that are conjoined… I was prepared to bury my children the day that they were born. And then they don’t die. I guess it was kind of a shock seeing them together – but I fell in love when I first saw them.” – Chelsea Torres, mum to conjoined twins Callie and Carter

This new two-part documentary for ITV explores the amazing world of conjoined twins, discovering how families cope with the extraordinary circumstance of being parents to the rarest of babies – one out of every 200,000 live births.

Narrated by Sheridan Smith, this documentary features three-year-old twins Callie and Carter from Idaho, who are fused from the chest down with two legs between them, and whose parents Nick and Chelsea Torres only have a few months left to decide whether to opt for separation.

They meet still-conjoined and now separated twins on their quest to make the best decision for their children. Cameras follow the work of leading British doctors at Great Ormond Street Hospital as they try to separate conjoined twins over four nail-biting operations.

And the programme explores the extraordinary lives of the twins still joined together around the world, including Krista and Tatiana who share so much of their brains they can see out of each other’s eyes.

With parents facing impossible decisions over whether t go for separation surgery, this documentary goes up close with the twins to discover what their unique relationships are like with their siblings – and how the dynamic works once they are no longer conjoined.