I have a question for vampire mythology fans. No young kids allowed.?

In the Buffy/Angel mythology specifically, vampires do have blood of their own (which is important, because in the "Buffyverse," in order for a vampire to "sire" another, they need to feed the victim some of their own blood). They don't have a working heart, so how the blood is transported down "there" is not readily explained (other than, for the amount of intimate relations the Buffy/Angel kind of vampires have, it obviously gets there SOMEhow). As far as the baby thing is concerned, in that specific case, a whole lotta magic and prophecy and whatnot was involved, because in that specific "universe" it's -supposed- to be impossible for a vampire to procreate via the "usual method" (i.e., sex).

I am a big fan of Buffy/Angel and don't recall them ever saying the vampires don't have blood running through their veins. I think it is accepted that they do have blood it just doesn't belong to them. The reason they need to feed in the first place is because they need blood running through their bodies in order to function. An erection would just be an extension of that, assuming he has fed recently a male vamp should have no problem having sex and this seems to be the case throughout most vampire lore as they are often said to seduce their victims.

The vampire pregnancy that occurs in Angel is, to put it simply, craaaazy. they do at one point explain how it happened but it is certainly not the norm in mythology. Vampires are said to be infertile in every historical source I've ever read and Twilight is not a source that should be considered even remotely "realistic". In lore a vampire "turns" or "sires" someone in order to have children, some vampires turn young children for that sole purpose but they never give birth.

I don't think they say that he has no blood in his veins. They do say he doesn't breath. Besides getting erections, vampires in the series bleed when injured. Without blood, they become pale and emaciated and suffer hallucinations. I always saw it as vampire blood being able to pass between the circulatory and digestive system in vamps and simply disintegrating over time (as they have no need to eliminate waste). This is why Buffy vamps can eat and drink food and alcohol, but don't need to, and how poison in blood the vampires drank hits their blood stream. In the Anne Rice novels, the vampires cry/sweat blood and their skin becomes pinker and more lifelike after drinking. I don't remember if they get erections. I don't know if this theory works for the Twilight series or True Blood or the Vampire Diary books, but I've never seen anything on the Vampire Diaries series that contradicts it. To me, the great problem with conception is lack of sperm - most series agree that vampires can't father or carry children.

Vampire pregnancy isn't a common event in BtVS/AtS lore. It was a one time occurrence, completely mystical in nature, and a mystery to the characters how it happened. I'm trying not to spoil anything here, but a god later claimed to have used the opportunity created when Angel endured a series of trials to save (human) Darla's life when she was terminally ill with syphilis as she had been when she was first human, but it was determined that she had already been given a second chance when Wolfram and Hart resurrected her, so her illness wasn't cured. She became a vampire again. Then, during Angel's lowest point of depression and anger at failing to save her, she and Angel slept together and a human baby, complete with a soul, was conceived.

I've read a lot of different vampire genre books. In almost all of them, getting an erection doesn't seem to be a problem. It varies vastly from book to book about impregnating someone. Although, in most it seems that a vampire female cannot get pregnant. I believe it's all in who the author is and what they want their particular vampire to be able to do. Like, some can't be in sunlight at all, some die immediately and some have no problem at all. It's all interpretation.

As far as the silver screen goes, the whole vampires having sex and impregnating people is a new thing. But for mythology the only case I can think of is the incubus. Its a vampire that seduced and impregnated women, most probably invented so that the unmarried women who ended up pregnant wouldn't be as shunned from society as they would have been. There was also a female counterpart (the succubus) that seduced men.

Most people see fantasy fiction as not having to make scientific sense.

More like authors and scriptwriters like giving their vampires quirky undead features, but don't want it to interfere with their sex appeal, so they disregard continuity when it comes to sex.