I think it started in the movie Underworld.
The story goes like this:
You see there was a man in Hungary that couldn't die or get sick. His two sons were different too, they were bitten, one by a wolf and the other by a bat.
The bat one was like a normal human but he was stronger, faster, he drank blood. The wolf one was entirely transformed into a wolf, he ate meat.
They both could transform people into their own kind. Werewolves couldn't have changed into human shape til one day a Lycan was born. Lucius was the first who could transform from wolf to man.
Vampires were more civilized and werewolves savage. Vampires took lycans as slaves and it was then the was started. Lycans rebelled against vampires and the war began.