I think his family spoke French at home when he was growing up.
Canada would be a lot different if more Quebeckers moved west to the prairies. Instead, a lot of them moved south into New England for the factory jobs. In contrast to other immigrant groups, they didn’t make a lot of noise or stir up much notice. They were pretty modest people, actually.
By the way, he has a very interesting history. He was born to a 16 year old single mom in Calgary in 1979. She put him up for adoption and the couple that adopted him were two teachers in Saskatchewan, Marlene and Donald Poilievre. They are from French-Canadian descent.
A couple of years after Pierre was born, his maternal mother got pregnant again and this child (Pierre’s half-brother) was also adopted by the Poilievre family. His maternal mom became a nurse and lives in North Carolina.