Welcome to Rootschat. I've moved your post from Ireland Resources board since that's a place to post resources not queries. Please remember that Rootschat isn't a forum for tracing people so you aren't allowed to post details of living people here. Also, typing everything in capitals is considered shouting and should be avoided since you won't want to appear rude.
Let's start with your granfather Christopher Ledwidge.
There are 6 Christopher Ledwidges in 1911 census but only two in Lucan D.E.D., Co. Dublin (Doddsborough townland)-
http://www.census.nationalarchives.ie/pages/1911/Dublin/Lucan/Doddsborough/3939/Christopher Ledwidge (age 44), wife Catherine (age 34), children John (11), Christopher (9), Mary (7), William (5), William (5), Joseph (4) and baby Annie. The census also says that Christopher and Catherine married c1894.
And in 1901 Christopher, Catherine and John are in Lucan-
http://www.census.nationalarchives.ie/pages/1901/Dublin/Lucan/Lucan_Petty_Common/1267688/The closest match I can find for Christopher's birth so far is a Christopher Ledwich born 11 June 1868, son of John Ledwich and Anne Comisky (they also had a son Simon Ledwidge born 23 July 1873).
Christopher's marriage certificate should list his father's name.