He was reportedly the son of Gwynllyw, a Welsh king, brother of saint Cadoc and the father of Beuno (died 640), abbot and saint. His wife Peren, Beren, or Perferen was the daughter of Lleuddun Luyddog, identified as King Lot of Lothian.
He married Beren, daughter of Llawden and they were strongly religious and lived quietly on the land given by his grandfather, but had no issue.
It is reported that when Bugi was dying he sent for his son Beuno, who came to him, and "After receiving the communion, making his confession and rendering his end perfect he departed this life." It was said that Beuno planted an acorn at the site of Bugi's death, which grew into an oak tree forming an arch; any Englishman passing through this arch would die, while a Welshman would be unharmed.
- Miller, Arthur (1885). "Beuno". Dictionary of National Biography, 1885-1900, Volume 04. Retrieved 11 February 2016.
- Baring-Gould, S.; Fisher, John (1907). Lives of the British Saints: Vol 1. Honorable Society of Cymrrodorion. p. 340.
- Sims-Williams, Patrick (2004). "Beuno [St Beuno] (d. 653/9),". Oxford Dictionary of National Biography. Retrieved 11 February 2016.
- "Saint Beuno Gasulsych". CatholicSaints.info. Retrieved 11 February 2016.
- "Gododdin". Heavenfield. Retrieved 11 February 2016.
- Saints of Newport-Children of Gwynlliw-St Maches of LLANVACHES St Cynydir, St Bugi.
- "St. Beuno Gasulsych". Early British Kingdoms. Retrieved 11 February 2016.
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