NEW YORK (CBSNewYork) — For the first time in its history, the TCS New York City Marathon will feature a set of quadruplets.

When Teresa Siemann got pregnant after a series of fertility treatments, doctors at New York Methodist Hospital in Brooklyn assured her she’d only have one.

“And when they did the sonogram there were four,” Siemann said.

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Sisters — Jessica, Maria and Amanda — and their brother, Brian, were born two months premature and weighed a combined nine pounds.

“Nothing can prepare you for it,” Siemann said.

When Brian was six days old, a mistake made in the hospital left him paralyzed for life.

“My doctor left my umbilical catheter open which caused me to lose a third of the blood in my body,” Brian said.

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Brian Siemann competes in the Rio 2016 Paralympic Games on September 14, 2016. (Photo by Atsushi Tomura/Getty Images for Tokyo 2020)

Brian Siemann competes in the Rio 2016 Paralympic Games on September 14, 2016. (Photo by Atsushi Tomura/Getty Images for Tokyo 2020)

The quads are 27 now and Brian is an elite wheelchair racer who managed to talk his sisters into doing a marathon he’s done five times already.

“It seemed just like the perfect opportunity to get the four of us to do a marathon because I don’t think we’re gonna be able to convince Jessica to do another one,” Brian said.

“They were all geared up and ready to go, and I was planning to just cheer and I got talked into it,” Jessica said.

Their parents will be watching in Sunset Park near the hospital where the quads were born.

The Siemanns are believed to be the first quads ever to compete together in the marathon.