The oldest known twins in the world say years of clean living and exercise helped them reach their 105th birthday on Tuesday.

One of the twins, Ellen Robertson of Winnipeg, taught aerobics until she was 93.

"Oh life is perfect," Robertson told reporters on Friday, sitting in a wheelchair with a yellow flower pinned to her blouse.

"I was lucky to be a twin. How many people get to be a twin? Not many."

Robertson and her sister, Sarah Jeanmougin, are recognized in the Guinness World Records bookas the oldest living twins.

They were born on May 29, 1902, in the town of Wolseley, near Regina. At the time, Saskatchewan was three years away from becoming a province, so the sisters' town was considered part of the Northwest Territories.

The twins' father died when they were just four. Four yearslater,their mother moved the girls and their eight siblings to Winnipeg.

The girls were always dressed in identical clothing growing up. Robertson said her sister, who now lives in Arizona, was always the cheerful one.

"She's happy all the time. You can tell from her pictures," Robertson said.

"Sourpuss me," she added, laughing as shepointed at herself.

Robertson kept active throughout her life, nevertouching a cigaretteand clocking an estimated 160,000 kilometres on her exercise bike.

The hour-long aerobics classes she taught at a senior's complex were notorious.

"People would come for only half an hour because they couldn't keep up with her," said her son, Dixon Robertson, who's 74. "She just lived a clean life."

Her outlook on life helped too, he said.

"Everybody's great, nobody's bad. It's just her attitude."