Courtesy John Maixner

John Maixner spent years walking into a Walmart in Dickinson, N.D., and waving to the friendly female employee who, he now can see, bore a slight resemblance to him.

It wasn't until Maixner, 57, who was given up for adoption as a baby, began looking for his birth family to obtain medical information that he discovered the Walmart employee, Buddine Bullinger, was his sister.

"My mouth just fell open," Maixner told GoodMorningAmerica.com today.

Since his search began last year, Maixner has discovered he has a brother and three sisters, and he's been reunited with all of them.

The children were all given up for adoption over 50 years ago by their mother through Catholic Services.

One of the children, Deidre Handtmann, who lives in Bismarck, reconnected with their mother later in life and took care of her until her death last year.

Bullinger, 56, knew their mother's name and was connected to Handtmann by the funeral home after their mother died. Catholic Services put Handtmann in touch with Maixner this summer.

When Handtmann told him about their other siblings and showed him Bullinger's picture, Maixner had his jaw-dropping moment when he recognized the Walmart employee.

Soon Maixner and Bullinger were making up for the lost time they spent as anonymous customer and employee.

"We exchanged phone numbers and went to Perkins and had coffee and got to know each other," Maixner said of his younger sister.

All five siblings - brother John Blankendall, in Tennessee, and Sandy Watkins, in California - met face-to-face for the first time in October.

"I walked in and I was just kind of speechless," Maixner said. "The conversation got going after a while, but we all just looked at each other and we all looked alike."

"I found myself looking at my brother and comparing our ears and our noses and our eyes," he said.

In just a matter of weeks, Maixner, who has no kids of his own and lost his adoptive parents last year, gained four siblings and "at least" 10 nieces and nephews, he said.

"I gained a huge family," said Maixner, the eldest sibling.

Now the five brothers and sisters are speaking by phone "every day or two" and celebrated Handtmann's 50 th birthday together earlier this year.

"We just talk about daily things," Maixner said. "What we're doing…work…what we're eating for lunch or supper."