An interesting genealogy of the Royal Family from John O'Hart's Irish Pedigrees (1892). A nice touch that it takes us right back to Adam, who was (as it sayth in St Luke his Gospell) the son of God.
Historically, I think there is a fairly good claim that the most ancient lineal descent of our Royal Family runs back through the patriarchal head of the Scottish royal house, Kenneth MacAlpin, to Fergus Mor MacEarca (see no. 90 on the list) who may have been a contemporary of St Patrick, and it is anyone's guess as to where the list prior to Fergus passes over from history into myth.
My own conviction is that Conn of the Hundred Battles (born in the fifth generation after Christ, c.200), has too cool a title to be written out of history; and it is cooler still that when a debauched man called Nero was president of the EU and the legions were building their horrid motorways all over the green English countryside, Ireland was ruled by a man called Fiacha of the White Oxen.