Born Thelma Mae Robertson to Scottish parents in Montréal, Québec,[2] she was the niece of Clark Griffith, a former star pitcher who became manager (1912–20) and then principal owner and president of the Washington Senators (1920 until his death in 1955).

Haynes' father, James Robertson, was a Canadian minor league baseball player who died in 1922, leaving behind a widow and seven young children.

In October 1955, Clark Griffith died at age 85, leaving his 52 percent majority interest in the Senators evenly split between Calvin and Thelma.

The family also included brother-in-law Joe Cronin, like Clark Griffith a Baseball Hall of Fame player (and later a manager, general manager and American League president), brother Sherry Robertson, who played, coached and served as farm system director for the Senators/Twins franchise, and two other brothers, Jimmy and Billy Robertson, who were also team executives.

Thelma Griffith Haynes relocated from Minnesota to Florida in 1982 and died at 82[4] on October 15, 1995, in Orlando, the team's longtime spring training home, after suffering a stroke.