Cornelius was born in 1866. Cornelius' father was Patrick Mangan and his mother was Johanna Foley. His maternal grandparents were James Foley and Catherine (Kate) Lyston. He had three brothers and a sister, named James, David, John and Bridget. He was the second oldest of the five children. He died at the age of 1 in March 1867. The funeral took place on March 21st, 1867.1