Two elderly, half-sisters who shared the same father met for the first time - and found out they are a lot alike.

"You'd be surprised by how much alike we look," one of the sisters, Zelda Gates, 85, told ABC News. "She brought some pictures and a couple of pictures of her as a teenager, I could have sworn up and down it was me."

Gates, of Jenks, Oklahoma, was home on May 18 when she got a call from someone asking if she was Zelda Gates and informing her that she was the niece of her half-sister, Reta Knight.

"I was absolutely shocked," Gates said. "I didn't know my father had been married before and had a daughter until my father passed away and they read the will, about 30 years ago, and it's been quiet ever since."

Gates and her brother tried to search for their half-sister when they discovered her existence, but it was back in the 1970s when looking for a long-lost relative was not as simple as going online.

Many years later, and just one state away, in Kansas, Reta Knight, 94, was moving from her home to a retirement community when she and her niece, Lesa Kleinmann, stumbled upon an old photo of Knight's mother and father on their wedding day in 1918, one year before her birth.

"She would say in the last few years, 'I just wish I knew more about my dad,' so that's why we got on Ancestry.com," Kleinmann, of Overland Park, Kansas, told ABC News.

Thought Knight had taken the last name of her stepfather after her mother remarried, the name on her birth certificate was Bourne, the last name of her father, William Bourne, whom she never met.

Through Ancestry.com, Kleinmann and her husband found Gates' nephew, whom Gates describes as "the keeper of the Bourne family history."

"When we thought we found something we called Zelda's nephew and started the story and he said, 'I think you should call Zelda,'" Kleinmann recalled. "A week ago Sunday I just decided to pick up the phone and thought, 'Well we're going to see what happens.'"

What happened is that Gates immediately invited her newly-found half-sister and her family to her home in Oklahoma, where, on Sunday, the two finally met.

"From the minute they saw each other, it was just really heartwarming," Kleinmann said. "They looked at each other and they were just smiling the whole time."

"There's not a better word than to say it was a miracle," she said.

The pair, who met on Sunday, spent two hours talking and poring over old photos they had each brought, with Gates filling Knight in on the life of the father she never knew.

"My aunt was so thrilled to see pictures of her father throughout his life, what he did, where he lived," Kleinmann said. "She was also really pleased to know that they [Gates and her brother] knew of her and had looked for her."

The only thing that remained unresolved after the sisters' meeting was why their father had not kept in touch with his eldest daughter, Knight, nor revealed her identity to his youngest daughter, Gates.

"We used to go visit my grandfather and my father's brothers and sisters and no one ever mentioned he had been married before or had a kid," Gates said. "And Reta's mother would never tell her anything about her father."

"Nobody knows why all the hush-hush about it and all of our folks are gone so there's no way of ever knowing," she said.

The pair did figure out, however, why Knight, who just stopped driving two eyars ago at the age of 92, is still so sharp and alert just months away from her 95 th birthday in July.

"We had always attributed to the fact that she was a nurse so knew how to take care of herself and didn't have any kids so had less stress," Kleinmann said. "But Zelda said, 'Well, no, it's because she's got the Bourne longevity genes.'"