Family and friends of a brother and sister taken too early by cancer turned the tables on grief Friday by celebrating what would have been the siblings' birthdays.

"Imagine — born on the same day," Major Lorne Pritchett said during the Mercer family's first annual celebration of life at the Salvation Army Corps Hall in Conception Bay South.

Alex and Riley Mercer shared the same birthday and, tragically, the same illness. Alex lost her battle more than a decade ago, at the age of nine; Riley passed away just five months ago.

Riley Mercer

Riley Mercer died five months ago from a rare form of brain cancer. (Courtesy Louise Mercer)

"Riley would have turned 16 today," his mother, Louise Mercer, told the gathering. "We had such big plans for Riley. He was supposed to write his permit today and we were supposed to buy him his first car."

Alex Mercer

Alex Mercer, Riley's older sister, died of the same rare cancer when she was nine years old. (Courtesy Louise Mercer)

The guests of honour may not have been there in person, but they certainly were in spirit, Pritchett said.

"Some people would say, 'should we celebrate their birthday?' I have to tell you in our faith tradition, they're having their birthday today."

The service was just one of several gestures to mark the anniversary.

Some of Riley's friends celebrated by shaving their heads to raise money for cancer research.

"I thought I'd shave for the brave because he's done so much for me in my life. He's made me happy for every single day," said Peter Garland.

A theme for the annual birthday celebration was also unveiled — the winning entry "S.O.A.R." coming from young Hayley Gosse.

It stands for Spirit of Alex and Riley.

"It has both their initials and it puts them in a special place," she said. "This means the world to me."

And to Alex and Riley's dad, Bernie, as well.

"So my dearest Alex and Riley, enjoy your birthday in the sky. Alex, you have Riley. And down here, I have your mother. Happy Birthday."

Lt-Gov. Frank Fagan and his wife Pat also attended the event, having lost their 25-year-old son, Richard, to cancer in 2012.

Friday's birthday celebration concluded with cheers and applause while dozens of balloons were released into a bright blue sky just before sunset.