They endured an risky 14-hour surgery.
For a young couple, the news that they're expecting twins is one of the most exciting things they could hear. But hearing that their unborn children are conjoined can be equally terrifying.
Despite the medical miracles doctors can pull off these days, it can still be difficult knowing your children will face an intense surgery that puts their lives at risk, along with other health complications.
This was just the situation Heather and Riley Delaney found themselves in years ago, when doctors at the Children's Hospital of Philadelphia (CHOP) confirmed their unborn daughters were joined together at their heads.
The girls, Erin and Abbey, were born 10 weeks before their due date by an emergency c-section. They weighed just two pounds each at the time,and weren't ready for the grueling surgery required to split them apart.
Along with skin, the twins were connected by blood vessels and brain tissue, meaning dividing them would be risky and extremely complex.
A team of specialists at CHOP spent the next 11 months preparing the girls, and when the day of their surgery finally came it took a full 14 hours to separate them. The procedure also made them record setters, as the youngest twins joined at the head to ever be successfully split.
In the months that followed, both girls underwent even more surgeries to replace parts of their skulls, and physical therapy to strengthen their underdeveloped legs.
But despite all of the extra care they needed, both at home and at CHOP, being able to cradle the girls on their own was worth it for the Delaneys.
Two years since the procedure, doctors say that Erin and Abbey are both doing well, and the Delaneys are continuing to share their story online so people around the world can support and encourage these tough little girls.
Twins joined at the head, called craniopagus conjoined twins, are some of the rarest in the world. About six sets of twins in 10 million are joined at the head.