There once was a couple, who both happened to be lycanthropes (specifcally werewolves). Naturally, their kids were both lycanthropes as well.
But, they were a poor family (this being the Middle Ages), so something had to go.
"Kids," the father announced, "I'm sorry but we're too poor to keep you. We've no choise but to sell you off as slaves."
So, with a bit of crying and puzzled farewells by the kids, the couple went off to the local town bazzare to...
...sell their weres (wares).