William was born on February 14th, 1892 in Youghal, Co Cork. William's father was Thomas Flavin and his mother was Mary Cronin. His paternal grandparents were William Flavin and Mary White; his maternal grandparents were Cronin and Mary. He had two sisters named Katie and Elizabeth. He was the oldest of the three children. He died at the age of 101 on September 2nd, 1993.