She was the daughter of James Connolly (b. 1844) and Catherine Fagan (b. circa 1850), Cavan natives who had married in 1871 before having a large family (possibly as many as eleven children). Kate's known siblings were: James (b. 1873), Nellie (b. 1877), John (b. 1880) and Mary Jane (b. 1898).
Kate appears on the 1901 census living at house 6 in Curtrasna and by the time of the 1911 census in house 1, Curtrasna. Her mother was a widow by the time of the latter census and Kate's age was listed erroneously as 19 and with no stated profession.
Kate decided to join her sister Nellie in New York and boarded the Titanic at Queenstown as a third class passenger (ticket number 370373 which cost £7, 15s). Her cabin mates aboard were fellow Cavan girls Julia Smyth and Mary McGovern and a girl from Co Clare, Mary Agatha Glynn.
On the night on the sinking Kate and her roommates made their way to the upper decks and were able to escape in lifeboat 13. She later reported that several of young Irish men had found a route to the upper decks before returning to show them the way. The presence of two Irish women named Kate Connolly on board Titanic initially caused confusion on both sides of the Atlantic; another woman, Kate Connolly from Tipperary was lost.
Kate eventually landed in New York and was reunited with her family already there. She was married in 1916 to William Arkins (b. 7 March 1890) who also hailed from Cavan and the couple settled in Manhattan and had four sons: James William (1919-1992), John Joseph (1920-2009), Peter (b. 1925) and Thomas (1926-1926).
Kate's husband James initially worked in a shipyard before they started buying properties to let out to tenants. Kate died in Whitestone, New York on 3 July 1948 following a stroke aged 60; her widower James died in 1963.