"Half one, half another. The best of both." - Aro's comments on hybrids.
Hybrids are unions of different species. It doesn't matter, as long as the creature were once human or is human, can the creation of a hybrid be made. It is stated that the mother must to be physical strong enough have Hybrid kids... Renesmee , Eve, Angelo, Tamal, Tamal's half-brother Nahuel , his sisters, Serena, Jennifer, Maysun, Eve's mother and sister, Esther, Andy, the rest of her Hybrid pack, Damien and Remy are all hybrids of different kinds, and some are more common then others. The most powerful and common types of hybrid are Vampire/Werewolf hybrids.
the half wolf and half vampire are a Celtic Species