Sisters Separated by Adoption Reunite by Chance at College and Now Celebrate Graduation With Birth Mother

Lizzie Valverde, 35, and Katy Olson, 34, were adopted separately as children.

— -- When Lizzie Valverde graduated from Columbia University on Monday, she had two special supporters in the crowd: her long-lost sister and their birth mother.

Valverde, 35, and Katy Olson, 34, met two and a half years ago, on the first day of a writing class at Columbia.

Both women already had a lot in common: they were returning to college in their 30s and both wanted to pursue their passion of writing. But that day, the women discovered something more -- that they are sisters.

And when Valverde graduated from the Ivy League school on Monday, Olson was there for support -- one year after her own graduation.

Valverde told ABC News that having her sister at graduation "felt amazing" because they met at Columbia. "So, to see the culmination of all of my efforts at this school ... to have her there and know that I'm walking away with the greatest story, it was wonderful to have her there. It just felt like everything was coming together."

What made the moment even more special, Valverde said, was her daughter got to walk up on stage with her to accept the diploma.

"It was great," Olson told ABC News today. "To see her graduate one year after I did was pretty incredible."

Olson called it a "culmination of a lot of really hard work," adding: "She was just trying to show herself and the world what she could do."

Valverde's graduation also marked an important occasion for Olson -- Olson met their birth mother, Leslie Parker, for the first time on Sunday.

Parker, 54, was a teenager when she gave them up for adoption. As children, the sisters were adopted by different families -- Valverde grew up in New Jersey while Olson was raised in Florida and Iowa.

Olson said when they met, she ran over and gave Parker a hug.

"I thought it went really well," Olson said. "She was very open and it was nice to get to speak with her."

"We were all talking and laughing," Olson said. "We talked about a wide variety of subjects ... my birth and why she wasn't able to keep me ... all the way to who's your favorite male celebrity."

Olson and Parker then sat together at Columbia on Monday as they watched Valverde graduate.

Parker told ABC News earlier over the phone that she, too, always dreamed of being a writer, but had never been given the chance.

"I'm so proud of them," Parker said. "They're both amazing, beautiful women."

And for Valverde, nothing could top having her daughter, family, sister and biological mother at Columbia on Monday.

"To see both my moms together -- that's a pretty intense moment," Valverde said. "With my family watching ... all the people in my life who've gotten me to that point -- especially my daughter -- was really humbling."

"It felt like all the things that matter in my life were very much there," Valverde said.