PHILADELPHIA — State Rep. Sara Feigenholtz arrived at the Democratic National Convention last week with one of her three sisters by her side, which in and of itself isn’t so unusual. Many delegates bring guests.

What made it most extraordinary was that until three weeks ago, the 59-year-old North Sider had never met her sisters.

For Feigenholtz, adopted at birth, the intervening days have been a whirlwind of self-discovery — the reunion made all the more poignant by Feigenholtz’s standing as a national leader on adoption issues.

“I always wanted a sister. Now I’ve got a bunch of them,” Feigenholtz told me one morning last week during an emotional interview.

OPINION

Feigenholtz had introduced me to her sister earlier. The resemblance was striking.

Having written some columns in the past about Feigenholtz’s adoption work, I was aware of her back story and understood the significance of seeing them together. So did many of her Illinois political friends, several of whom cried.

Feigenholtz had long known she had sisters, having tracked down her birth mother when she was in her 20s. She learned then that a year after putting Sara up for adoption, her mother had married and gone on to have three more daughters.

The mother raised her family a mile from Feigenholtz’s own childhood home near Peterson and Kimball before getting divorced and moving back East.

Over the years, she told Feigenholtz her sisters’ names, which allowed her to secretly learn more about them through Facebook.

But her mother forbade Feigenholtz from contacting her sisters because some family members remained unaware of the out-of-wedlock birth, often a source of shame and scandal in the period Feigenholtz was born. Her mother promised Feigenholtz that if she died, one of her sisters would let her know.

Feigenholtz was scrolling through her emails June 21, waiting to go to a Cubs game, when her heart skipped a beat as she recognized the name in her inbox as one of the sisters she had never met.

“I was in shock,” Feigenholtz told me, first assuming her mother had died.

But as she read on, she learned that wasn’t the case. Her sisters were seeking permission to visit her in Chicago.

They came to town July 7 and did all the tourist stuff — Millennium Park, a Sox game wearing Cubs T-shirts (the Cubs weren’t in town), and a river cruise on which the tour guide told the story about how the Windy City doesn’t get its nickname from the wind but “because all the politicians are full of hot air.” In a welcome display of sisterhood, her sisters booed the guide in unison.

But the best part of the trip may have come when they took a walk near her home and ran into a neighbor, who marveled at how much they look alike, and asked if they were sisters.

“It was the first time in my life that ever happened,” Feigenholtz whispered, still cherishing the moment. “It was the first time in my life that ever happened.”

When Feigenholtz got to Philadelphia, she and her sisters went to lunch with their mother.

I wish I could show you the photo of the meeting, or the photo I took myself that first morning at the hotel — both a lesson in genetics, with all of them having the same large expressive eyes and something sly happening around the mouth.

But the East Coast daughters don’t want to betray their mother’s privacy, which is why I have not mentioned any names.

For Feigenholtz, who makes it her mission to open birth records to help adopted children learn more about their biological parents, it’s all good.

“They have said we want you in our lives,” she said. “We want you in our family. You couldn’t ask for anything better.”