Two sets of sisters who learned they are related through DNA testing are speaking out on their surprising discovery.

Twins Kristelle Harrington and Rachelle Dyer, 53, and sister pair Lisa Holley Vann, 51, and Shannon Nicholl, 49, stopped by "Good Morning America" on Tuesday to share their story.

"Lisa and I had no idea at all that our mother had even given birth to twins in the past," Shannon said live on "GMA." "They knew that they were adopted all these years -- so for us, it was pretty mind-blowing."

In the 1960s, Kristelle and Rachelle were adopted by loving parents when their birth mother couldn't take care of them.

Across the country in Virginia Beach, sisters Lisa and Shannon were born a few years after Kristelle and Rachelle. The women never suspected their family might be bigger than they thought.

In 2004, Rachelle moved from Seattle to Virginia Beach -- where Shannon and Lisa were living.

Coincidentally, Rachelle became friends with the same group of women who were friends with Shannon. The two were eventually introduced through a friend who said they looked alike, but no one had any idea they were related.

In 2009, Rachelle and Shannon were both going to a Kenny Chesney concert with their mutual friend. They met briefly at the show and took a photo together. That was it for about 10 years.

"The crazy thing was, the two friends that were telling [Rachelle] we looked alike were my childhood best friends," Shannon said on "GMA."

Rachelle said, "And when we looked at each other we were like, 'Wow, this is kind of like looking in the mirror.'"

In 2017, Rachelle’s husband had her take an ancestry DNA test to find out more about her ethnicity. She got the results in March 2018. She says she never thought about looking for DNA matches at that point.

A few weeks ago, Rachelle decided to look for DNA matches after the principal at the school where she works encouraged her to since they were working on an ancestry project.

She checked the DNA connections and made contact with a cousin named Tracy, who told her she has two half sisters in Virginia Beach, including Nicoll. Rachelle realized she had met Shannon before –- at the Kenny Chesney concert.

On Feb. 6, Lisa, Shannon and Rachelle met for dinner in Virginia Beach. A week later, Kristelle arrived from Seattle and all four sisters meet for the very first time.

A DNA test confirmed all four women were born to the same mother, Janice, who had put the twins (Kristelle and Rachelle) up for adoption in the Seattle area after deciding she couldn't provide for them. A few years after she put the twins up for adoption, Janice got married and had two daughters in Virginia Beach.

Rachelle said her one regret is that their birth mom wasn't around to see this.

"I feel like I was a year-and-a-half too late because that's when our birth mom passed away," Rachelle added. "All four of us feel like she's had a big hand in this. Getting us all together at this time in our lives. We all really needed it. I've never had my own family in Virginia Beach. And Lisa and Shannon don't have the mom they grew up with there anymore."

VIDEO: 4 long-lost sisters reconnect live on 'GMA'
VIDEO: 4 long-lost sisters reconnect live on 'GMA'

"But I like to think that now they have two new piece of her in me and Kristelle," she said.

The sisters hope to spend holidays together from here on out.