Iorwerth was the son of Gruffydd ap Heilyn and Mallt verch Einudd. The date and place of his birth have not been found.
He died after 1276. The place is not known.
His wife was Tangwystl verch Gruffudd. They were married, but the date and place have not been found. Their three known children were Gwladys verch Iowerth (?-?), Efa verch Iorwerth (?-?) and Gwen verch Iorwerth (?-?).
| Event | Date | Details | Source | Multimedia | Notes |
|---|---|---|---|---|---|
| Death | AFT 1276 |
|