Tanglwystl was the daughter of Iorwerth ap Ednyfed and Angharad verch Ieuaf Fychan. The date and place of her birth have not been found.
Her husband was Adda ap Awr Trevor. They were married, but the date and place have not been found. Their two known children were Ieuaf ap Adda (?-?) and Eva verch Adda (?-?).