Ross was born January 13, 1885, in Naughton, Ontario.[a][c] His father, Thomas Barnston Ross, was of Scottish descent and originally from Chicoutimi, Quebec, while his mother was Marguerite (Margaret) McLeod. Ross's parents initially lived in Lake St. John, Quebec (now Lac Saint-Jean), where Thomas worked for the Hudson's Bay Company (HBC). The family had ten children: nine sons and one daughter.[d] Around 1876 Thomas was transferred to a trading post in Northern Ontario close to the Whitefish Lake. Living in a remote outpost, the family would trek 370 kilometres (230 mi) each way twice a year for supplies.
Ross spent his early years at the trading post, and first learned to skate on the nearby lake. He grew up speaking English, and was taught French by his mother, and later in life claimed he knew Ojibwe and Montagnais. In 1892 the family moved back to Lake St. John, though in 1895 Margaret left Thomas, and moved back to Ontario with her younger children. She married Peter McKenzie, who was the Chief Factor for HBC in the region (and thus Thomas' superior) in 1895. They moved again in 1896, settling in the affluent Westmount district of Montreal. Thomas also re-married, and by 1904 was living in Victoria, British Columbia, where he died in 1930.
In Montreal Ross attended Westmount Academy, and became active in a variety of sports, though he was best at hockey and (which was still very similar to at the time). He likely first played organized hockey in the 1900–01 season, joining the Westmount Amateur Athletic Association. With this club he first met the brothers Lester and Frank Patrick, both of whom were later inducted into the Hockey Hall of Fame. Ross and Lester had a financially successful ticket resale business at the Montreal Arena, buying tickets for thirty-five cents and selling them for up to a dollar.