Young adult twins suffer extremely rare strokes just months apart

In what appears to be an exceptionally rare set of circumstances, 26-year-old Arizona twin sisters both suffered strokes nine months apart.

It is a coincidence so rare doctors say the odds are the same as a person being struck by lightning -- twice.

"We are super close," Kimberly Tucker tells ABC of her twin Kathryn Tucker. "I think we always have been close, but this definitely brought us closer."

While previous research suggests there is a fivefold increase in the prevalence of stroke among identical twins compared with fraternal twins, Kathryn and Kimberly are fraternal twins.

Kimberly suffered a stroke on the left side of her head this April. Last July, just nine months earlier, Kathryn suffered a stroke on the right side of her head.

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When Kathryn had her stroke, Kimberly quit school to take care of her. So when she experience similar symptoms to her sister, she knew exactly what was happening and took blood thinning medication immediately.

"My vision closed in almost completely," Kimberly says of the fateful day. "I wasn't making a lot of sense and was not able to form complete thoughts. But I knew I was having a stroke."

As for Kathryn, when she suffered her stroke last year, her symptoms were dismissed as a migraine with an aura. She was sent home from the emergency room without medical intervention.

"I was absolutely terrified," says Kathryn."I slept for three days straight. Then, when I woke up, my vision was horrible. Everything was distorted and one-dimensional. I could barely get around."

Her health continued to deteriorate, so she went to an urgent care facility. From there, she was sent to a neurologist who diagnosed a stroke.

Multiple things about this situation that have stumped doctors. Despite the fact that the twins have a family history of stoke, they were both exceptionally young to experience one. And again, because they are fraternal twins, they do not share the same DNA.

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"Honestly, it's rare for us to actually evaluate two sisters who've had strokes within months of each other," says Dr. Joni Clark, a vascular neurologist at Barrow Neurological Institute in Phoenix.

That said, there were a number of preexisting conditions specific to each woman that made them more susceptible.

Kathryn was a smoker at the time and had stopped using birth control a few weeks before. She also had a PFO, or patent foramen ovale, a small hole in the heart that doctors believe may have contributed to her stroke.

And Kimberly has arrhythmia, an abnormal heart rhythm, which again doctors believe may have been a contributing factor to her stroke.

To this day, both their medical conditions have improved after occupational and speech therapy, though they still have some visual deficits and are not allowed to drive.