I found a reference to a John Davis, married to a Jane Davis with a son Robert Davis, aged 13. This would match our Grandfathers birth date of 1898.
His address was 14 in Liberty Lane (Mansion House, Dublin). The whole family was Church of Ireland and literate.
In 1911 Robert was 13 and had a 16 year old brother George and 24 year old sister Mary. George was a doctors page, Mary a hotel waitress and Robert was a scholar (in school). John Davis the father was a carpenter.
Have a look at http://www.census.nationalarchives.ie/pages/1911/Dublin/Mansion_Hou....
Is this our great grandfathers family?