Laurence was born on February 18th, 1848 in Dublin City and his baptism took place on February 18th, 1848 in St. Nicholas Dublin conducted by priest S A Farrell. His godfather was Thomas Stanly and his godmother was Mary Byrne. Laurence's father was James Hannon and his mother was Anne Byrne. He had two brothers and a sister, named Daniel, John and Bridget. He was the second youngest of the four children.