In the first installment of Underworld, Viktor (one of three vampire elders) and Singe (a lycan scientist/biochemist) are having a conversation regarding Michael Corvin and why the Lycans needed his blood so badly.
Singe: A direct descendant of Alexander Corvinus...Hungarian, a warlord... who came to power in the early seasons of the fifth century. Just in time to watch a plague ravage his village. He alone survived. Somehow, his body was able to change the disease...mold it to his benefit. He became the first true immortal. he fathered at least two children...who inherited this same trait.
Viktor: The sons of the Corvinus clan.One bitten by bat, one by wolf...one to walk the Ionely road of mortality as a human. - It's a ridiculous legend!
Singe: - That may be...but our species do have a common ancestor. A mutation of the original virus...is directly linked to his bloodline.
Viktor: There is a descendant of Corvinus lying there...not three feet from you!
Viktor states that the sons of the Corvinus clan is a ridiculous legend. One was actually bit by bat (Marcus Corvinus) and another by wolf (William Corvinus) creating the first of the vampire and lycan species. Viktor is well aware of this. He was turned into a vampire by Marcus Corvinus himself. This is who he is referring to when he points out to Singe that a descendant of Alexander Corvinus is lying three feet from him.
So, why would Viktor say that the sons of the Corvinus clan is a ridiculous legend?