What began as a simple bit of family tree research led Mary Brand of London, Ont., to find a half-sister she didn't know she had in England, the result of a liaison her father had while serving overseas during the Second World War.

And while it's the kind of family secret that could have caused discomfort had it been discovered earlier, Brand and her family couldn't be happier.

"It's like a gift," she said. "It's like a little bit of my father that's come back. I haven't seen him for 56 years and all of a sudden, there's more of him. It's wonderful."

Brand, a 73-year-old retired teacher, opened an Ancestry.com account in 2006 to track down some loose threads in her family history.

She knew of course that her father, bomber captain John Norman (Jack) Harris, had served in the war and played a role in one of its most famous prisoner-of-war camp escapes.

Mary Brand with a photo of her father John Norman (Jack) Harris, who fathered a daughter while serving overseas in England before he married Brand's mother. (Andrew Lupton/CBC)

In 1942 Jack Harris's plane was shot down during a raid on Hamburg. He spent the rest of the war at the Luftwaffe-run Stalag Luft III POW camp in Poland.

A group of prisoners famously broke out of that camp in 1943 by using a wooden gymnastics vaulting horse to conceal an escape tunnel. Harris was not among the three who escaped. The episode was made into the 1950 movie The Wooden Horse.

After the war, Jack Harris returned home to Canada with his wife Aileen Dunkeld who he married in 1942. They had four children together and he began a writing career that would lead to him becoming an acclaimed author. He died in 1964.

Brand knew all this history but what she didn't know is that in 1939, her father had a liaison with a woman in Torquay — a seaside town on the English Channel. It happened while he was there recovering from injuries suffered in a plane crash. Soon after they met he returned to action, likely unaware of the pregnancy.

Online research reveals secret

Fast forward to March of last year.

After some time away from the website, Brand logged back on to find an unfamiliar face pop up on her computer screen. The website had flagged a woman named Rilba Jones as a possible first cousin to Brand. The website allows users to submit DNA information after providing saliva samples. The database uses that information to identify users' relatives.

It didn't take long for Brand to figure out that Jones, who was born in 1940 and six years her senior, wasn't her cousin, but her half sister.

"Let's just say I looked at the dates and put two and two together," she said laughing.

A Google search revealed that her half sister is a retired city councillor living in Hull, England.

Mary tried to initiate a conversation over email but Jones didn't respond at first, fearing she was the target of an Internet scam.

Eventually Mary's daughter Alicia made contact with Jones's daughter Harriett. Working together, they discovered this was no scam and that their mothers where half sisters who had been completely unaware of each other's existence for more than 70 years.

Family secret kept hidden

Shortly after she became pregnant, Rilba Jones's mother married a man named Blair White. He was also a pilot in the war who was killed during the invasion of Sicily in 1943. He died believing that Rilba was his biological daughter. After all, her unusual first name (Rilba) is an anagram of his own (Blair).

And while Brand was shocked to learn that she had a half sister, Jones had known for years that her mother had harboured a family secret.

Jones made the discovery as a young girl after she was confined in a back room for misbehaving. While serving her punishment, she found an old diary of her mother's at the bottom of a locked trunk (she'd picked the lock). A diary entry revealed details about her mother's first pregnancy.

Rilba confronted her mother. Instead of getting an explanation, she was admonished for snooping and told never to speak of it again. For decades to come, she didn't.

She didn't disclose it to anyone in her family, including her husband, until she became a grandmother.

Sisters meet for the first time

After Mary and Rilba connected online last spring, they corresponded and decided to meet in person.

Mary travelled to Hull in October. The two hit it off right away, just like like sisters.

"We get along really well," said Brand. "I do see a lot of similarities."

A literary strain certainly runs through both sides of the family.

Two of John (Jack) Harris's more famous books: Knights of the Air and The Weird World of Wes Beattie. The latter was an acclaimed mystery novel published shortly before his death in 1964 at age 49. (Andrew Lupton/CBC)

After the war Jack Harris became a well-known writer who counted among his friends such Canadian literary figures as Pierre Berton, Farley Mowat and Morley Callaghan.

He wrote for many periodicals and his acclaimed mystery novel, The Weird World of Wes Beattie, was published shortly before his death. His book Knights of the Air, about Canadian World War I pilots, was a staple in school libraries.

Mary's only surviving full sibling, John R. Harris, is a speech writer and Rilba's daughter, Harriet, is a journalist.

The two half sisters correspond regularly and Mary believes her father never knew his brief affair with Rilba's mother resulted in a pregnancy.

Mary Brand's mother Aileen died in 2005 avoiding what would likely have been an uncomfortable revelation, even though the affair that produced Jones happened before they were married.

"It's made it easier that there's no one around to have funny feelings about it," said Brand. "We can all laugh about it and enjoy it and celebrate it."