It's the kind of encounter that can only happen in Ottawa.

Gov. Gen. David Johnston says his grandchildren sometimes run into the children of Prime Minister Justin Trudeau when they're playing on the grounds of Rideau Hall.

Johnston, who represents the Queen in Canada, lives on a 79-acre park nestled near the Ottawa Rivier. He's a landlord of sorts to the Trudeau family, who moved into a cottage on the grounds of Rideau Hall as the government prepares to renovate 24 Sussex.

The Trudeaus, Johnston says, are very good tenants.

"It's wonderful because their children play in the garden where our grandchildren play and it's pretty exciting to have the next generation together bringing the place alive," he said in an interview with Robert Fife, host of CTV's Question Period.

Johnston's wife, Sharon, has become good friends with the Trudeau family, he said, noting the relationship dates back to when the prime minister was growing up.

"We had two of them there [the] day before yesterday, and Sharon and the family have become good friends. And our friendship with Mr. Trudeau goes back to children's days when our five daughters and he and his two brothers skied together at Mont Tremblant," he said of the ski resort in the Laurentian mountains.

Johnston knew Trudeau's father, former prime minister Pierre Elliott Trudeau, when Johnston was vice-chancellor of McGill University in Montreal. He says he and the rector of the University of Montreal tried to recruit Pierre Trudeau back to a joint appointment at the two schools.

"His three boys were the same age as our five daughters so we were kind of a ski party from time to time at Mont Tremblant," Johnston said.

"Our children had enormous respect for Mr. Trudeau senior. He was ... a wonderful father and very good with children."

Johnston said he and Justin Trudeau are still figuring out their meeting schedule as Governor General and prime minister after nearly a decade of monthly meetings with Stephen Harper.

"We're still establishing our rhythm," he said.