Angela and Dennis Laffin adopted him and named him Frank.

In 2002, someone left a newborn baby boy in a diaper bag on the front steps of Bellamy’s Christian Daycare on Staten Island, New York.

Angela and Dennis Laffin adopted him and named him Frank.

They already had a biological son, Nick. And Frank turned out to be a handful. He was allergic to almost everything and barely ever slept. So when he was just a few months old, the Laffins decided their family was complete.

Angela called the adoption agency to close their file.

But while she was on the phone, she casually asked about a baby girl she’d heard about in the news.

A cardiology technician named Claudia had found the newborn in a bathroom at Richmond University Medical Center, also on Staten Island. She was wrapped in a blanket and tucked under the toilet tank.

By the time Angela hung up, she had told the caseworker they would take her.

Then she went and told her husband.

They named her Victoria.

Frank and Vicky grew up a year and a half apart. People constantly asked if they were related, and the Laffins always said no.

As it turns out, Claudia, the woman who found Vicky, became one of Angela’s close friends. Vicky grew up knowing her, but didn’t learn until she was 18 that Claudia was the one who had found her.

Then, as adults, Frank and Vicky decided to take DNA tests to learn more about where they came from.

Frank’s results came back first. Some Italian, some English. Nothing surprising.

Then Vicky’s results arrived. And her top match was Frank.

They shared between 49 and 56 percent of their DNA.

They were full biological siblings.

Vicky called her mom screaming so loudly that Angela thought she’d been in a car accident.

“Of course you’re brother and sister,” Angela told her. “I raised you.”

“No, Mom,” Vicky said. “You don’t understand.”

Two babies, abandoned in different places 18 months apart, and somehow they ended up in the very same home