Upon the death of William Donn de Burgh, 3rd Earl of Ulster, the various factions of the de Burghs, now called Burke, began a civil war for supremacy among each other. The factions were headed by Sir Ulick Burke,(d.1353); Sir Edmond Albanach Bourke ,(d.1375); and Sir Edmond de Burgh of Castleconnell (k.1338), ancestor of the Bourkes of Clanwilliam in Munster.

Ulick was a great-grandson of Richard de Burgh , the illegitimate son of William de Burgh. He was the head of the Burkes based in Upper Connacht , what is now Co. Galway.

Edmond Albanach was the son of Sir William de Burgh , also know as William Liath Burke , who was the grandson of Richard Mor via his son, William Og, who was killed at the battle of Athanchip in 1270. He was the leader of the Bourkes based in mid and Lower Connacht, in what is now Co. Mayo .

Edmond of Clanwilliam was the fourth and youngest son of Richard Og, the 3rd Earl. Married to Slany ni Turlough O'Brian King of Thomond, he was based at Castle Connell in Limerick.

The eventual outcome of the war was the fragmentation of the de Burgh family into three distinct clans, all of which had several sub-septs. Ulick became the head of what was known as the Clanricarde Burkes of Galway, their title stressing their descent from William's son Richard. Their alternative title was Mac William Uachtar, i.e. the Upper Mac William. They became Earl of Clanricarde in 1543, a title held in the family till the death of the 15th Earl in 1916.

The Bourkes of Mayo fell under the leadership of Edmond Albanach, known as the Mac William Iochtar , i.e., the Lower Mac William. This title would be held by successive descendants of Edmond Albanach up to the 1590's.

Edmond of Clanwilliam was captured, jailed, starved and ultimatly drowned in Lough Mask in 1338 at the instigation of Edmond Albanach. However the Bourkes of Clanwilliam survived and prospered in Munster under the leadership of his sons, Richard Bourke of Castle Connell and Walter Bourke of Ballybourneen .

Genealogical Relationship of Clanricarde, Clanwilliam and Mac William

 William de Burgh, c.1160?-1204.
 |
 |_______________________ _ _ _ _ _ _ _ _ _ _ _ _ _ _
 |                                             |
 |                                             |
 Richard Mor, c.1194-1242.                     Richard
 |                                             |
 |_______________________                      |
 |                     |                       William Ban  
 |                     |                       |
 Walter, c.1220-71.    William, k.1270.        | 
 |                     |                       Richard
 |                     |                       | 
 Richard Og, d.1326.   Sir William             | 
 |                     |                       Sir Ulick Burke 
 |                     |                       | d.1353.  
 Sir Edmond Bourke Sir Edmond Albanach         |
  of Clanwilliam       | d.1375.               |    
     k.1338.           |                       Clanricarde Burke
        |        Mac William Iochtar              of Galway
        |             of Mayo
        |
 Clanwilliam Bourke 
    of Limerick