In 2001, Lexi and Sydney were born conjoined twins. Now, they’re about to separate for good.

On March 9 2001 Lexi and Sydney Stark were born conjoined at the spine in Colorado. Seven months later, the pair underwent life-threatening separation surgery, and against all odds, they survived.

Now sixteen years after their surgical separation, the family is sharing their story.

The twins’ parents, Emily and James Stark, knew that their daughters were going to be conjoined prior to the birth, they shared on Monday’s episode of Megyn Kelly Today.

A doctor recognised something unusual in an ultrasound, and unfamiliar with the condition, brought out a 1000 page medical book, in which there were two small paragraphs on conjoined twins.

"[The doctor] looked at us and said 'they're joined somewhere in the lower region'," shared Emily Stark, adding that when she heard the news she tuned out and stared at the ceiling, allowing her husband to take over.

"I knew in my heart we would have twins, it was one of those gut things," she added.

According to the program, 1 in 50,000-60,000 births result in conjoined twins.

40-50% are delivered stillborn, with another 35% surviving just one day.

Despite the odds, the conjoined twins' parents said they never doubted that their children would survive.

"Oh Lexi are you having a nightmare? A nightmare that your sister is stuck to your butt?", the father joked in the delivery room.

Since conventional clothing wouldn't fit the twins, for the first seven months of their life Sydney and Lexi would share onesies. Logistically, they would each put two legs through one leg hole each.

Despite the twins being healthy when they were conjoined, their parents made the decision to separate them.

Two weeks prior to the surgery, Emily Stark asked her husband whether they were "playing God", as their daughters could die in the surgery.

As they said goodbye to their daughters, they knew that following the surgery they might only have one, or both might have died.

Miraculously, Sydney and Lexi who are now 17 years old have no major health problems, but they do say they experience twin telepathy.

When she was five or six Sydney was getting a painful injection at the hospital and to her mother's surprise, showed no signs of pain.

Moments later, her father called. Sydney's twin Lexi was in hysterics at home, screaming out in pain.

The twins added that sometimes they sense that the other is having a bad day, before they have even spoken.

Most touching though, is the sleeping position that the twins adopt. They shared that when they have stress naps, they naturally end up in the same position as when they were conjoined.

"Being by her… it’s so calming," said Lexi of the position.

Sydney and Lexi will soon separate permanently for the first time, as they are applying for universities in different states, but something tells us their connection knows no boundaries.