Boyle, County Roscommon
Cryan was the son of Robert Cryan and Mary Anne Cryan of Boyle, County Roscommon, Ireland. He had two sisters, Mary Anne and Belinda, two half brothers, Peter, (also a doctor), John, and a half sister, Bridget. He was married to Mary Whitty, daughter of Nicholas and Mary Whitty, and had one son, a writer, Robert William Whitty Cryan. Cryan died at age 54 at his home in Dublin on 17 February 1881 and left a "considerable fortune" to his family. Cryan is buried at Glasnevin Cemetery in Dublin.