BUFFALO, N.Y. — It's the photo that's launched a 21st century search. 

On February 3, Matt Wilmore, a Buffalo native now living in San Antonio, called his sister to check in. She gave him some unexpected news. 

Their mom passed away in 2016 and, in going through some of her journals, Wilmore's sister found passages with "themes of regret" and the revelation that they have an older sister. 

The baby, Melanie Joy Wilmore, was born in January 1972 at Buffalo Children's Hospital to a young unwed mother.

"She had a very conservative family," Matt Wilmore says. "She was sent to some home for women who were single and pregnant," and the baby was taken to Our Lady of Victory Infant Home, known today as Baker Victory Services. 

Wilmore took action, posting what little information he had to Twitter. 

Within days, the post had racked up more than 9,500 retweets and hundreds of messages of support. 

For those who question whether this is an invasion of privacy for the sister he's never met, Wilmore offers a counterpoint. 

"Maybe this person is out there looking for you as well," he says. 

There are a few hurdles that could make the search more complicated. 

"The unfortunate thing that we run into often is that in New York, adoptions are sealed," said Kelly Gorkiewicz, a program coordinator at Catholic Charities.  Any identifying information cannot be shared without explicit permission. 

To secure that permission, or to obtain identifying information, a person can register with the state's Department of Health as someone who was adopted, or as the sibling or parent of someone placed for adoption. 

If both parties register, the state can contact the agencies involved to provide information. 

Still, Wilmore will continue his search and has some words for his long-lost sister: "You're part of the family, so we love you."