Catrin was the daughter of Gruffydd ap Llywelyn and Ragnhild verch Rheinallt Skjolding. The date and place of her birth have not been found.
Her husband was Iowerth Vychan ap Iowerth. They were married, but the date and place have not been found. Their only known child was Iowerth Voel ap Iowerth (c1242->1313).