LITTLE BRAS D’OR, Nova Scotia — John Brennick opened a box in his antique-filled house here to reveal a sleek sealskin pouch that a forefather stuffed with precious papers more than a century ago. On a nearby table lay the most important document: an 1818 land grant from Britain’s King George III, its wax seal still bright orange and largely intact.

There is no doubt that Mr. Brennick’s ancestor, Francis Young, existed, and there is little about who he was: a prosperous resident of Indian Village, as Nova Scotia’s Little Bras d’Or was once known, who Anglicized his name in order to win the land grant.

Assuming a British identity helped him avoid the fate of his indigenous kin who were being crowded onto reserves. But erasing his native heritage also deprived generations of his line from enjoying treaty rights as Indians, the name by which Canada’s First Nations are still legally called today.

Many of Mr. Young’s descendants are lobbying now for recognition as Mi’kmaq, the indigenous nation on Canada’s Atlantic coast to which Mr. Young had ancestral ties.