A set of conjoined twins in Canada have defied the odds of survival after learning how to walk, talk, and even argue like siblings do. Tatiana and Krista Hogan, 7, of Vernon, British Colombia, who were not expected to survive the day they were born, share a special connection: Their brains are “zipped together.” As a result, the twins are able to hear each other’s thoughts and see what the other is seeing.

Tatiana and Krista’s mom, Felicia Hogan, was given the news that the twins’ future looked bleak while she was pregnant. However, in the Channel 5 documentary titled “Joined at The Head: Twin Life,” Hogan emphasized abortion “was not an option.” The twins have been monitored since birth, as doctors are marveled by how their shared brain works.

“They have amazed me — how they are the same but how they are different, how they are dealing with an error of nature to live healthy lives,” said Dr. Douglas Cochrane, a neurosurgeon who has treated the girls as they’ve been growing up.

The girls were born craniopagus conjoined twins, meaning they are joined at the top, back, and side of their heads. Their shared brain structure consists of a neural bridge between their thalamus, which regulates consciousness along with sensory and motor signals. It is with this shared brain tissue structure and the interconnected neurons that one brain receives signals from the other brain and vice versa. This means one twin can “see” what the other twin is seeing, which makes them even more unique within craniopagus twins.

This type of conjoined twins is very rare, accounting for only two percent of conjoined twin births. Upon delivery, the twins were described as wriggly, vigorous, and very vocal, weighing 12.5 pounds, according to the B.C. Women's Hospital & Health Centre news release.

The girls can also share thoughts and communicate within their own heads. The twins’ grandfather explained: “They start giggling and you know they're up to something and they haven't said a word. Pretty soon after, they will go and pull a prank and you know they are communicating, we just don't know how."

Although they feel the same things, they have different personalities. “Over the years Tatiana has become the prominent leader,” Hogan said. In fact, in the documentary, Tatiana exclaims, “I'm the red Power Ranger: Jason! The leader.” Krista, on the other hand, is “quieter and can be more in her own shell.”

Unfortunately, the twins will never be able to be separated or live independent lives because of the way their brains are fused together. Hogan described it as this “one big zipper that can't be unzipped.”

“We tell them, ‘You two have to spend the rest of your lives together in this world, you need to cooperate and be nice to each other.’”