I have a thery on that. We know that in the time of the ancesters there were a lot of pb's, and now there are very few, I belive we can tell why the ancesters are so strong comapired to the new borns just by looking at what is going on in the story now, we have a vampire with desires going around trying to feed on the other pb's, we have seen them do this in a desire for power, kaname, rido, sara, and shizuka (she wanted to but didn't get the chance) all of them have done it so far so if they are doing it now then why not back then?
This might also explain the whole protecter of the pb's title cause if they were hunting each other to gain power chances are sooner of later they would have all died and aparently it is a big enought crime for 1 pb to feed on another (to the point of killing them) for kaname to hide that he did it even thought the one he feed on was considered a dangerous vampire.
So long story short maybe the reason the ancesters are so strong is not cause they were born first but cause the toke power from the other pb's.
What is every one elses take on this?