Background

Diarmaid was the son of Madudan Reamhar Ua Madadhan

Madudan Reamhar Ua Madadhan

-Biography:A grandson of Gadhra Mór mac Dundach and a son of Madudan mac Gadhra Mór, Madudan Reamhar was the first bearer of the surname Madden, a family originally from east County Galway....

 (died 1096). In addition to ruling Síol Anmchadha

Síol Anmchadha

Síol Anmchadha was a sub-kingdom or lordship of Hy-Many, and ruled by an off-shoot of the Ui Maine called the Síol Anmchadha , from whom the territory took its name....

, he was the last of his dynasty

Dynasty

A dynasty is a sequence of rulers considered members of the same family. Historians traditionally consider many sovereign states' history within a framework of successive dynasties, e.g., China, Ancient Egypt and the Persian Empire...

 to gain overlordship of Uí Maine, ca. 1134.

Ua Fuirg and Ua Ceannéidigh

In 1131 he was responsible for the slaying of Domhnaill Ua Fuirg, lord of Uí Forgo. This led to his own death in 1135 by Gilla Caoimhin Ua Ceannéidigh, to whom Ua Fuirg was a dependent. He was succeeded by Cú Coirne Ua Madadhan, who ruled from 1135 to 1158.

Family

The names of Diarmaid's spouses and partners do not seem to be recorded. He is listed as having the following male issue:

• Madudan Mór Ua Madadhan
  Madudan Mór Ua Madadhan
  Madudan Mór Ua Madadhan, King of Síol Anmchadha, died after 1158.No details of his era appear to be known.-References:* http://www.ucc.ie/celt/published/T100005B/...
  
  , who became chief in 1158
• Murchadh
• Conchobhar, whose son Murchad became chief of half of Síol Anmchadha
  Síol Anmchadha
  Síol Anmchadha was a sub-kingdom or lordship of Hy-Many, and ruled by an off-shoot of the Ui Maine called the Síol Anmchadha , from whom the territory took its name....
  
  , and died in 1201
• Maelsechlainn Ua Madadhan, chief from 1158 to 1188.

A poem described Diarmaid as without weakness or error.