In reality, two vampires, regardless of their bloodline and origin, would not be able to make children. There were hearsays that royal blood vampires or pure ones could give birth, but that was actually not true.
A vampire's body was dead. They were able to live due to the magic of life provided by blood. They do have a long life that was close to immortality. However, Heavens are fare. If vampires could procreate just like humans, then there was a high chance that vampires had already ruled the world.
That was not the case at all. Since they could not give birth or create life themselves, they were dependent on humans to exist. It was basically like the animal kingdom.
Vampire kills humans to live, but they also need humans to continue livings. A very interesting cycle if one would be thinking of this more.
