I'll say it to you again, no Tenkai (other than Thomas - but he was a "break away" Tenkai) has ever known both parents (or either parents for that matter in some cases) - so the Prince not knowing his Dad isn't a big deal.
I made that post before the "information" was revealed - though it likely is fact, we don't know that it is official information.
Still, the point stands, when we didn't know any information about his dad, that wasn't anything special whatsoever as the previous Tir, Riou, Hugo and Hero4 have not known all (or any) or their parents.
and it is never said that hero 4 dident know his father ..hero 1 lived with his dad hero 2 was adopted and hero three well there are 4 of the not inculding luc so one of them must of known there father
Actually, the Tenkai of Suikoden 3, Thomas by the way, did know his father but not very well and was abandoned. And Hero 4 most obviously did not know his father. He was abandoned to see as a very small child. Although, they do hint at who his dad is throughout the game.