N.N. ap Judicael - N.N. ap Judicael birth date

You have N.N.'s birth date listed as about 580 and his brother Selyf as about 575. You list his fathers as about 599 (matches Wikipedia) and his grandfathers as about 580. That puts both being born before their father and the same time frame as the grandfather. I know circa means about but there is no way this can be correct. Any changes in birth dates could cause a problem with the birth dates for several in the line before or after the date change.
It also list St. Judicael ap Hoel's father as Hoel III (it seems correct by the way they used names at that time), Wikipedia list him as the eldest son of Judael or Judhael, King of Domnonée, and Queen Prizel. Which is correct? I know Wikipedia is not always correct and info from the time frame is hard to come by.