In terms of basic biology, Hexenbiests seem to be the most atypical species, and there are indeed hints that they don't belong to the same category of beings as the others. When two different types of Wesen have a child, that child will be whichever type is dominant over the other.
The chance of two Kehrseite-Genträgers having a Wesen child is unknown. Two humans or a human and a Kehrseite-Genträger cannot have a Wesen child. If a human and a Wesen have a child, there is a fifty percent chance that child will be a Wesen. If two Wesen have a child or a Wesen and a Kehrseite-Genträger have a child, there is a one hundred percent chance that child will be a Wesen. Because of this, Wesen genetics are very complicated. Woged Wesen always shift back to human form when they die.Įach Wesen, no matter the type, possesses two sets of DNA in each cell. All Wesen possess the ability to identify Grimms when in their woged state because when a Grimm looks at a woged Wesen, their eyes turn black with their pupils being an image of the Wesen. This second type of woge is usually invisible to normal humans, who continue to perceive the Wesen in his or her human form but it is visible to Grimms. Although they can woge voluntarily, most Wesen also experience an involuntary woge triggered by emotional states such as stress or fear. The process of shifting from one to the other is known as "woging". Wesen are liminal beings, and have two distinct forms, as they alternate between a human form and a creature form.