William mór de Burgh, 2nd Baron of Connaught

According to FMG Medilands, Richard & his wife [Egidia] had seven children. One was;
"g) WILLIAM de Burgh (-killed 1270). The Annals of the Four Masters record in 1270 disputes between “the king of Connaught...and...the Earl” during the course of which “the Earl´s brother (William Oge, son of Richard, the son of William the Conqueror” was taken prisoner and later “put to death...by O´Conor”[485]. m ---. The name of William´s wife is not known. William & his wife had one child: WILLIAM Liath".

http://en.wikipedia.org/wiki/William_Og_de_Burgh

William Og was ancestor to the Earl's of Clanricarde, the Mac William Iochtar, The Bourkes of Mayo, and after the extinction of the de Burgh creation of the Earldom of Ulster, the de Burgh line.

Sir William Og de Burgh

had one son:

Sir William the grey/ Liath de Burgh, d.1324

Sir William the grey, in turn, had three sons:-

--Sir Edmond Albanach de Burgh, 1st Mac William Iochtar/ Lord of the Lower Mac William, d.1375.

--John de Burgh (1350-1398) Theologian, Chancellor of the University of Cambridge

--Sir Ulick de Burgh, Lord of Clanricarde (d.1352) 2nd Mac William Iochtar. Ancestor of the Earls of Clanricarde.

Sir William Óg was the third son of Richard Mor de Burgh, Lord of Connacht. De Burgh served with distinction in France with King Henry III in 1245 and later in Scotland. He was involved in fierce feudal warfare in Ireland where he killed the Lord of Desmond. He was killed at the Battle of Áth an Chip or Athankip by the Ua Conchobair Kings of Connacht, in 1270.[1]

He was survived by at least one son, Sir William Liath de Burgh, Custos or Warden of Ireland, who married Una, a daughter of the Mac Jordan of Connacht, and died in 1324. William Óg was thus ancestor the Mac William Iochtar, the Bourkes of County Mayo.