Krista and Tatiana Hogan can do things that nobody else can do.
They share the senses of touch and taste and can control one another’s limbs.
Tatiana can see out of both of Krista’s eyes, and Krista can see out of one of Tatiana’s. Tatiana controls three arms and a leg, and Krista controls three legs and an arm.
They have different personalities - one of the girl's is very confident, while the other is a very gentle soul. But what they share is something no one else in the world has ever experienced.
Mamamia's Jessie and Clare Stephens talk twins. Post continues after podcast.
Krista and Tatiana are craniopagus twins, which means they are joined at the head. Their brains are connected by a thalamic bridge, which acts like a switchboard relaying sensory and motor signals and regulating consciousness. This means that their two separate brains can behave as one.
"They can sit there and not say anything to eachother, and all of a sudden one of them will pop up and grab something to eat for the other one. Like, there's no words being spoken between the two of them at all, and they know exactly what the other one wants," their mother Felicia Simms told 60 Minutes Australia in 2012.
"You can tickle one, and the other one laughs. You pinch one, the other one will cry with her like she's feeling it," she added.
While speaking to CBS, Felicia explained that it "actually takes a lot more effort for them to see things through eachother than feel things". And the girls can decide when they'd like to control the other twin's movement, or taste what they're tasting.
Krista and Tatiana were born on October 25, 2006, in Canada and are now teenagers. Their mother was just 21-years-old when she gave birth. The twins have an older brother and sister, and went on to have a younger sibling rounding out their family of seven.
It took 16 medics to deliver them safely into the world, with the twins given just a 20 per cent chance of survival. A CT scan has shown they can never be separated due to the risk of serious injury or death. They each have their own organs, but their vascular system works as one with their blood pumping through one girl into the other.