Henry Mckitterick Knockbridge Louth Ireland

This man was my great-great-grandfather and lived next door to where I grew up, but although himself and his family are on the 1911 census, they do not appear anywhere on the 1901 census, and i wonder why??? He married Mary Jane Finnegan in about 1877. They had 8 children according to the 1911 census, 7 of which were Elizabeth (Lizzie) married Callan, Mary Anne (USA), Julia (De Boer) Westchester Ave, Ellycott City, Maryland, USA., Bridget (b1887) married my grandfather Patrick Hoey about 1919, Patrick (b1889), Owen (b1891), Rose (b1893).