McDowell and McMinn

My Great Grandfather Daniel McDowell married Grace Nelson McMinn in 1869 ( 17 Feb) in Drumbo . Marriage shows Daniel’s father was Robert McDowell. 
I have been trying to find out more about Daniel’s birth and his family . 
Think he was born about 1826 as his death cert gives his age as 70 . He died in Waterford in 1897. He had a career in railway locomotive engineering  : was in Jamaica with his first wife Susan Curry (from Northumberland ) and daughter Margaret Jane , born in 1861 in Jamaica . He returned to Ireland in 1866 but wife died on passage home and I think young daughter Margaret may have gone to live with her mother’s relatives in England as she lived and married in Staffordshire.
His second marriage to Grace McMinn shows him as a widower. Daniel and Grace moved to Waterford and he worked for Waterford - Kilkenny railway and became the Superintendent. They had several daughters and one son , Daniel (my grandfather) who had a career with the Royal Navy mainly in England. 

Any information on Daniel’s links to Drumbo would be welcome . We have found out very little except he was from a Presbyterian family and father was Robert. 

Also on Grace McMinn (1840-1922) . Her father was Joseph McMinn and from Drumbo. Mother ? Magill.