Charlaine Harris' Southern Vampire series (Sookie Stackhouse novels) is a fun romp into a world where vampires, werewolves, fox-women and fairies co-exist with regular folks, though it's weakened quite a bit by the author's habit of throwing in explicit sex scenes.
One book tells the tale of how telepathic barmaid Sookie's friend Amanda the witch unintentionally turns her boyfriend Bob into a cat during some 'adventurous sex' (not described.) Amanda and Bob the cat, New Orleans residents, go to stay with Sookie in northern Louisiana and have to stay longer than planned when Hurricane Katrina hit.
At one point in Amanda and Bob's stormy relationship Amanda goes out into the woods looking for Bob and finds him with a female cat who is nursing a litter of kittens. Said kittens all look like Bob.
Later Bob is changed back to human, but nothing more is ever said about the kittens. They are half-human after all. What will become of them now that their human parent has bugged out?
That makes me wonder about the origins of werewolves and similar shapeshifters. In most werewolf tales, a werewolf gets that way by being bitten by another werewolf. But who bit the first werewolf?
I like the idea that shapeshifters might arise when a witch transforms a human into an animal, and that animal reproduces in animal form. Surely the child of a human, even a transformed human, will inherit the human essence/human soul.
In Asian culture, by contrast, the fox people (gumiho, kitsune) arise when a fox, who normally live only 12 years, lives to the age of one thousand. There's also a magical being that arises when a household object such as a teapot or a sandal becomes one hundred years old.
In Wildmage, there are shapeshifters. What happened was this: the original settlers of the elemental world (Wildmage world) came through portals from our world. They came from different points across the scope of human history (and landed within a hundred year span of the elemental world's history). Among those from the latest period were some who were humans with animal DNA, or animals with human DNA. On contact with the mage energies of the elemental world's environment, they all became shapeshifters who can be full animal, full human, or take the change-form (like the Wolf Man in the movies, hairy man-shaped dude with claws).
Later on, the lizard-men who settled in the central region of Zmaray got stuck in their change-form permanently, but that's another story.