Mildred Keller Tyson was Helen Keller's younger sister. Mildred Keller would marry Laban Warren Tyson, and would reside in Montgomery, Alabama. The Tysons had three daughters: Little Mildred, Patty Arrington, and Katherine Keller. Helen wrote her letters frequently which is a sign of their long lasting friendship. She died in 1971, at the age of 80.