Carpenter was born on March 2, 1950 in New Haven, Connecticut, the daughter of Agnes Reuwer (née Tatum) and Harold Bertram Carpenter. When she was young, she enjoyed playing baseball with other children on the street.

On the TV program This Is Your Life, she stated that she liked pitching. Later, in the early 1970s, she would become the pitcher on the Carpenters' official softball team. Her brother Richard developed an interest in music at an early age, becoming a piano prodigy. The family moved in June 1963 to the Los Angeles suburb of Downey.

Karen Carpenter's Family Tree