A human-vampire hybrid, also known as half-vampire, vampire hybrid and half-immortal, is the result of the successful mating between a female human and a male vampire, and conceive a spawn that shares many traits of both species.
Male vampires have the capacity to pass on genetic material with a human female partner. However, it is beyond the ability of most vampires to be so close to a human physically and still resist the lure of his/her blood. So far, the only known hybrids are Megan Cullen, Nahuel, and Nahuel's three half-sisters, Serena, Jennifer, and Maysun.
The whole process is extremely risky and can easily fail due to the fragile human body.-To conceive a hybrid, a male vampire will interact with a human female sexually. It is highly dangerous for the human in all ways. As the vampire will have a hard time resisting his urge to kill the human, it takes a high level of self-control to succeed.- When the human is impregnated, the fetus inside will grow inhumanly strong over time. Should the fetus cause too much traumatic damage to the mother before birth, it can easily destroy its own existence by killing its mother.
Once the fetus grows old enough and too big to remain in the mother's womb, it will utilize its own strength and teeth to break its way out. This will, however, result in the death of the mother, as the damage is too much for the body to take. The only way to save the mother after the fetus's birth is by injecting vampire venom into her body and change her into a vampire. So far, only Bella Swan has survived this process and become a vampire.
They are incredibly beautiful throughout their whole growth from infant to adulthood. Due to their rapid growth, hybrids reach full maturity at the age of seven, with the looks of someone of the age of seventeen. As with vampires, they have well-developed physiques and smooth, flawless skin, which is paler than a human's but not as pale as a vampire's. In sunlight, human/vampire hybrids do not glitter as vampires do, but appear slightly luminous, a feature that allows them to blend in more easily with human beings even during bright days. Due to their beauty and superhuman abilities, they may be mistaken for immortal children from afar.
Biology and traits
Vampire hybrids have both human and vampire traits.
Unlike vampires, human/vampire hybrids have a functioning heart with blood flowing through their system. They can sleep like human beings. They are capable of eating and gaining nourishment from both human food and blood, though they prefer blood, particularly human. Their body temperature is unusually warm, just a few degrees below that of shape-shifters.
Unlike vampires, their skin shows a weak illumination upon exposure to sunlight instead of sparking like diamonds, which makes it easier for them to blend in with humans.
Hybrids do possess the sweet scent of vampires but to a lesser extent (Renesmee's scent can be described as being as tempting as a human's). This gives them a unique scent all their own, balanced between being both appealing (as a human's) and sweet (as a vampire's).
They have 24 chromosome pairs, but it is unknown whether this is due to a sampling error or chromosome rearrangement. It seems, however, unlikely that they have any relation to the shape-shifters' chromosomes. There has been speculation that Renesmee and Jacob may reproduce, but there is not enough information to decide one way or the other.
As with shape-shifters, hybrids are a blind spot in Alice's vision. This is later explained to be due to the fact that Alice has never experienced life as a shape-shifter or a hybrid, and therefore cannot relate to it.
It is currently unknown whether hybrids can reproduce or not. It may be possible that they are able to, since the primary limitation for female vampires is their inability to change - not the case with hybrids. Even at full maturity, hybrids are able to digest normal food, an additional sign of an active metabolism. Like male vampires, Nahuel produces sperm, though eventual children have not been mentioned.
Human-vampire hybrids grow rapidly early in their life, reaching full maturity at approximately age seven, when they physically appear about seventeen years old and cease aging, as demonstrated by Nahuel's lengthy life of over 150 years with no further apparent change. Nahuel's oldest sister, Serena, is known to have lived for over 200 years.
Powers and abilities
They are supernaturally much stronger and faster than humans, with sharper senses, but are not as strong, fast, or sharp as a pure vampire (Esme described Nahuel as "not quite as fast nor fluid in his run as the vampires with him"). Like the hybrid's amniotic sac, her/his skin is almost as durable as a vampire's. They have perfect memory recall and develop mentally at a rate far faster than their chronological and biological age, speaking in complete sentences and walking just days after birth.
Renesmee is so far the only hybrid to show supernatural gifts, which she has inherited from her parents. It is unknown if other hybrids also show them, or if they are inherited or uniquely their own.
So far, no known hybrid females have been shown to be venomous, though Nahuel, male, has; it is unknown if this is generalizable. Despite both male and female hybrids showing the supernatural healing capacities of vampires, in such a case as an injury like dismemberment, only male hybrids may perhaps 'repair' themselves as completely as vampires. Since the known females apparently lack the venom necessary for the process, it may be supposed that their healing is not as extensive as males, and they would not survive such an injury. There is, however, a recurring idea about hybrids and the venom they produce. Female hybrids, such as Renesmee and Nahuel's three sisters, may have received prominent traits from their human mother, hence their lack of venom. Nahuel seems to have received most traits from his vampire father, which would make him venomous. It would appear that a venomous hybrid has the same venom-based fluids throughout their body as a full vampire. Non-venomous hybrids may have them to a lesser degree (as they have the sweet-smelling scent of vampires). Nahuel, a venomous hybrid, may display the same scent that full vampires have, without even a hint of human blood (his recently turned aunt Huilen was not tempted by the scent of his blood).