Tatiana and Krista Hogan were not expected to survive infancy. The conjoined twins were born attached at the head.

"We didn't know if they were going to survive 24 hours," their mother Felicia Hogan says. "And then 24 hours went by and they survived."

Tatiana and Krista celebrated their 11th birthday last October.

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"For them to actually be here for 10 years is just a blessing," Hogan told HuffPost Canada in 2017. "It just felt so good to see them get to this milestone."

A documentary about their lives,  "Inseparable: Ten Years Joined At The Head," which aired in Canada last year, follows the Irish Canadian family for a year leading up to the twins’ 10th birthday party. Along with the twins, Felicia and husband Brendan are raising Rosa (15), Christopher (13), and Shaylee (9). The family lives in Vernon, British Columbia.

Craniopagus twins are a one in 2.5 million rarity. 

Krista and Tatiana share a “thalamic bridge” that connects their brains. They are able to see through each other’s eyes, taste what the other eats, and know each other’s thoughts without speaking.

"The abilities they have that no one else could imagine having are just incredible," Hogan said. They play together, and without saying a word, get up when one decides she wants to do something else.

The twins’ doctor, pediatric neurologist Dr. Juliette Hukin, said: "They're the only twins that I'm aware of who are alive and remain conjoined with this shared connectivity.”

Judith Pyke, director and executive producer of the documentary, said: "It was cool to hear from them about how they can see through each others' eyes or move each others' limbs. But just as striking is they get along incredibly well."

BC's remarkable Hogan twins demonstrate some of their unique neurological capabilities. https://t.co/iTjBYywqnT
… pic.twitter.com/hbR4ppYnMl

— CBC Docs (@cbcdocs) November 5, 2017

However, the girls do have their “off moments” and are “definitely different” in personality, says their mother.

Krista likes to play pranks and make people laugh. She also tends to take charge. Her sister Tatiana loves cuddling animals and wants to hug everyone.

The girls love running around outside. They play video games, and they’ve learned to swim.

The girls, who are diabetic and have epilepsy, need daily insulin injections, take a regimen of pills, and need frequent blood tests.  Despite these challenges, they are able to go to school for a few hours every day.

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"They're just little people that are here living their lives like the rest of us," Hogan said. "That's how we see them and that's how their siblings see them."