A: What a great question. Children certainly do bond with pets and it’s adorable to see them together. The good news is that once you move I would not be surprised if your son does not notice the pet absence as much as you thought.
I do advise letting him know that "kitty" will be living in a new home but I'd keep the conversation brief and factual. Once you move, if your son asks about the cat’s whereabouts, remind him the cat is happy and in a good home. You might want to keep a picture of the cat somewhere to reference if he asks, but he will look to you as a guide, so model that you are coping well and he likely will too!