Usually, one genetic makeup wins out over the other, and in the case of witch and werewolf half-breeds, they are counted among the species whose traits they share most.
In the case of witches and vampires, when lamia marry and mate with witches, their offspring will be either-or; their children will be either a lamia vampire or a witch, regardless of the parents (such as in the case of the daughters of Hunter Redfern - a lamia - and Maeve Harman - a witch. Their three eldest daughters, Garnet, Lily and Dove inherited their father's lamia genes, whilst their youngest daughter, Roseclear, inherited her mother's witch genes). When a vampire changes a witch into one, although the witch will retain their own powers, he or she is counted as a vampire due to their new physiology and his/her new vulnerability to wood rather than iron. Many lost witches are technically hybrids, due to believing themselves human and intermarrying with humans.
While witches, shapeshifters and werewolves can successfully mate and produce children with humans (despite this normally leading to execution under Night World law for all involved), for lamia this is allegedly not possible; however, the existence of the vampire-human hybrid Jezebel Redfern throws doubt on this.
Half human hybrids are seen as "freaks" and believed to pose a threat to the Night World, and are often hunted down by Night People, as per the law. This is likely because the existence of such a hybrid usually means that one of the cardinal laws of the Night World - to never fall in love with a human - has been broken.
- Jezebel Redfern (only known successful product of a coupling between a vampire and a human. An exception to the dominant genetics rule, Jez has attributes of both humans and lamia vampires and is therefore the truest example of a hybrid in the series).
- Mal Harman (stated explicitly to be a vampire-witch hybrid, the first of the series. However, the scope of his abilities is still unknown).
- Lupe Acevedo (says she is not a "pure bred werewolf", as her father was human. However, as far as we know she exhibits all the usual abilities of a normal werewolf - it is unknown if she could choose to live as a human, in the same way as Jez Redfern).
- Raksha Keller and Rashel Jordan (revealed to be the twin offspring of a human mother and shapeshifter father. Interestingly, one twin - Keller - was born a shapeshifter, whilst the other - Rashel - was born human, though her notable agility and keen senses may be a sign of her mixed heritage).
- All known 'true' hybrids (Jez and Mal) in the series are half-vampire.
- The Wild Power prophecies foretold that one of the Wild Powers would be a hybrid: One from the Day World where two eyes are watching.