Ólafur Guðröðarson - Father Son birth dates

That does stink some, but it could just be a clerical or transcriptional error. The old records were handwritten (if not oral) and can be very hard to read or lost in translation sometimes. Printers also make loads of mistakes (I know because I worked for one, plus I often find errors in published books). So although inconsistent chronologically, on paper, they ''could'' still be father and son.