Iowerth Goch ap Maredudd (c.1110 - c.1171), a minor Prince and nobleman of the Kingdom of Powys, was the illegitimate son of Maredudd ap Bleddyn and Cristin ferch Bledrus. The appellation "Goch", meaning red, probably referred to the colour of his hair.
Iowerth married Maud de Manly, who gave him two sons, Gruffydd Vychan (c.1150), and Hywell ap Iowerth He had one brother Hywel ap Maredudd and two half-brothers, Madog ap Maredudd and Gruffydd ap Maredudd.
"[T]his brother, Iorwerth son of Maredudd, was extremely agitated and distressed at seeing the honour and power that Madog enjoyed, while he himself had nothing. He sought out his comrades and foster-brothers for advice, and they decided that some of them should go to Madog and ask for maintenance for Iorwerth. Madog offered to make his brother head of his troops, with equal rank, honours, arms and horses..." 
- "The Brief Life of Gruffudd ap Maredudd". Ancientwalesstudies.org. Retrieved 2012-05-09.
- "Treswell, Robert; Vincent, Augustine, ca. 1584-1626; Camden, William, 1551-1623; Grazebrook, George, 1831-1917 ed; Rylands, J. Paul (John Paul), b. 1846 joint ed; College of Arms (Great Britain)". Retrieved 2012-05-09.
- Burke, B. "Cherleton - Baron Cherleton of Powys" in "Genealogical History of the Dormant, Abeyant, Forfeited, and Extinct Peerages of the British Empire" pp.113-116.
- Bartrum, Peter C., Welsh Genealogies AD 300-1400,University of Wales Press, 1974
- "The text of the Mabinogion : and other Welsh tales from the Red Book of Hergest : Rhys, John, Sir, 1840-1915 : Free Download & Streaming : Internet Archive". Retrieved 2012-03-24.