What Liu Yang said was true. When a member of the blood race drinks the blood of a human, the two were closely linked. As a master and servant, or husband and wife depending on the case.
Normally, men of the blood race drank the blood of virgin women while women drink the blood of women and men, as a last resort. But each of them had a different criterion for drinking the blood and did not choose any for that.
Vampires were different, they were beings who drink blood from any type of individual, whether human or animal. They just like to drink blood and follow that instinct. Some had refined preferences while others were crazy bloodthirsty. Vampires also could create servants by drinking the blood of a human or animal.