Henry Gillman was born on November 16, 1833, in Kinsale, Ireland. He was of Irish and English ancestry.
His father, Edward, was a son of Henry Gillman of Belrose and Rock House; his mother, Eleanor Mandeville, a daughter of Capt. John Hackett, H. B. M. 8th Light Dragoons.
A line of descent from Adam Winthrop, lord of the manor of Groton in Suffolk and grandfather of Gov. John Winthrop of the Massachusetts Bay Colony, linked him to America’s beginnings.