When Paula O’Brien and Abbey Donohoe met at a party four years ago, they found they had a lot in common. Passers-by even said the two looked like sisters. And they were close to being right.

Thanks to a Facebook post made by O’Brien last week, Donohoe discovered that the woman at the party was her aunt by birth.

Donohoe was put up for adoption after her birth 29 years ago, and the Facebook post by O’Brien — forwarding a Davenport mom’s blog about living as a birth mother — noting the anniversary of the birth caught the Bettendorf woman’s attention.

“I was like, ‘Oh my God, it’s me,’ ” Donohoe recalled Tuesday, sitting on the couch at O’Brien’s home in north Davenport.

Off of Facebook’s public “wall,” the two exchanged private messages and quickly determined that they were related.

The youngest of five children, O’Brien found out on her 11th birthday that her brother had fathered a child. “It was quite a birthday present,” she recalled. And she remembers crying upon learning that the baby was being put up for adoption.

“I was heartbroken. I was so ready. I was the youngest one in the family, so I wanted another girl around the house.”

Every year, she and other family members would commemorate the birthday of the girl they didn’t think they would see again.

“It stayed with me all my life,” O’Brien said. “I just always had this sense that she was out there. We’ve always observed her birthday, always had plans to find her. I wondered, ‘Does she look like me?’ ”

After going to college in Arizona, O’Brien returned to the Quad-Cities and began work in 2000 as a reporter and news anchor at WQAD-TV, going by Paula Perez.

She tried to find records of her niece, but they couldn’t be made public because it was a closed adoption.

Donohoe knew the last name of her birth father, but since O’Brien didn’t share her brother’s last name, Donohoe didn’t make a connection when they met in 2009.

O’Brien’s brother now lives in Tennessee with three children of his own. Coincidentally, it was only six weeks ago that he informed his children they had an older half-sister. O’Brien said he was excited, having never expected he’d hear from the girl again. Donohoe’s biological mother lives on the West Coast and has been informed of the connection as well. O’Brien said neither of them wants to comment on the story, preferring that the attention be on their biological daughter.

Donohoe’s birth grandmother is excited to see the 29-year-old as well.

When O’Brien called with the news, “all I had to do is say one line to my mom and she lost it,” O’Brien said. “She said, ‘I’ve prayed for this day. It’s a miracle.’ ”

Raised as an only child, Donohoe will join a dozen cousins in her biological family.

She had thought of trying to find out more about her birth parents, but didn’t actively pursue their whereabouts.

Over the past few years her adoptive mother, Dee Ann, had encouraged Donohoe to learn more, and she had already begun taking an interest in doing so within the past year.

“She felt like it was necessary now, as old as I am,” Donohoe said. “She didn’t want me to date anyone I might be related to.”

Donohoe said her adoptive mother is excited about the discovery and supportive of all that has happened. They and O’Brien are scheduled to meet for lunch later this week.

“She definitely wants to meet people and be involved, too. If I’m happy, she’s happy,” Donohoe said of her adoptive mother.

Both the aunt and niece have been part of Quad-City Music Guild productions. O’Brien played a lead role in “Anything Goes,” and Donohoe has credits that include “Little Women” and “Seussical.” She’s also been cast in “Cabaret” this summer.

Donohoe, who graduated from Pleasant Valley High School and the University of Iowa, works as a dental hygenist in Davenport. After leaving TV news, O’Brien became a real estate agent, married and is now a stay-at-home mom to an almost-3-year-old daughter and a 10-year-old stepson.

After finding answers to such issues as family medical histories, Donohoe is looking forward to meeting more of her biological family.

Ever since they first met, “we joked around that we were sisters. We have very similar personalities, similar sense of humor,” O’Brien said. “We just kind of ‘got’ each other.

“The fact that this person has been right before my eyes for four, five years is just amazing,” she added. “It feels like I got a little sister. This is not a niece, we’re closer than that. The beauty about it, too, is that we are so alike and get along so well. It’s a huge blessing.”