I would have your sister take Ben to a different vet and get another opinion, when my Ginger was diagnosed with a brain tumor there was no blood work or anything like that, that could diagnose it, the only thing is either a cat scan or an mri, but i warn you they are very expensive. It sounds like to me he is having siezures and possibly does have something to do with the brain, before they diagnosed mine she did all sorts of weird things.
I really will pray for the best, I know this is horrible for your sister not really knowing what is going on.