When Montreal MP Justin Trudeau stepped into the ring Saturday night for his charity boxing match against a Conservative senator, it was with a saddened heart.

Trudeau's grandmother, Kathleen Sinclair, died Thursday at a B.C. nursing home.

"At 92, Gramma's mind was still strong, but her body slowly shut down," Trudeau said Saturday morning on Twitter. "She loved, and was loved, immensely."

Sinclair, born Kathleen Bernard in 1920 in B.C.'s Okanagan region, was part of a family steeped in politics.

Her husband, James Sinclair, served as a member of Parliament for the Vancouver area from 1940 to 1958, including a stint as fisheries minister under Prime Minister Louis St. Laurent.

Her daughter Margaret, one of five girls in the family, married Prime Minister Pierre Trudeau in 1971. Kathleen Sinclair was one of only a handful of people who knew in advance of the secretly planned wedding, and told CBC News at the time that she was delighted to have the prime minister marry her daughter.

"I was very happy for her because I think it was what she wanted," Sinclair said. 

Sinclair's 11 grandchildren include Justin Trudeau, the MP for the Quebec riding of Papineau, his brother Alexandre (Sacha), and Michel, the youngest of the three Trudeau brothers who died in an avalanche in 1998. She also had 13 great-grandchildren and four great-great-grandchildren, according to her obituary.

"Kathleen led a remarkable life," the obit reads. "Although she travelled the world, moved her family back and forth to Ottawa during the political years, her heart always remained in B.C."

Justin Trudeau's bout against Tory Senator Patrick Brazeau, to raise money for cancer research, will go ahead Saturday night at an Ottawa hotel. The three-round fight is one of several amateur matches at Fight for the Cure event, which has sold out.