Whose fault is this?, for years my nephew has been inviting me to come live with him?

I finally came, I noticed rat droppings here and there, I've been here since last friday, I went to the grocery store and bought about 200 dollars of groceries, and rat blocks, when I was unloading and putting it all away, his son stole the rat poison thinking it was maybe toys, he's not yet 10, this morning, turns out, he fed it to the dog, six blocks are missing, I've been trying to keep that boy and another out of my room for this very reason, do I have to pay the vet? I have been being nice to them, and not rude to these kids, I'm out of money, I'm supposed to start working next week.