I need some advice...?

So my brother is a hoarder basically, but he lives in a country where hoarding isn't really considered a crime. So after I homed a few cats, there are 4 left over. He says that two of them are mine, but two are his, even though all four are in my name. I vaccinated, spayed/neutered them, etc. They were here before I came, but he didn't feed them on time, take care of them, kept them outside. He even broke one cat's leg out of anger, and ended up putting her on the street, as he did with many cats. So I'm moving away from him, and I need to take all the cats with me. How can I do this in such a way where he won't know I took his 2 cats, if you can call them his? If I leave them there, I know he will neglect them, he says that kitty litter causes cancer so cats must be kept outside, etc. I just need someone smart and clever to give me a way I can take the two cats, but to make it seem like they went away on their own or something? He's having a birthday party pretty soon, so should I take them then? Just need advice, thanks.