John was born on March 2nd, 1851 in Dublin and his baptism took place on March 2nd, 1851 in St. Nicholas Dublin conducted by Nicholas O'Farrell. His godfather was William Hinch and his godmother was Elizebeth Rutledge. John's father was James Hannon and his mother was Anne Byrne. He had two brothers and a sister, named Daniel, Laurence and Bridget. He was the youngest of the four children.