Sounds like a quite ordinary dream to me
Would you think it was ok to harm frogs when they're big and ugly? What were your thoughts in the dream about your brother's intention? It doesn't have to mean anything special, unless you find a clear meaning of the dream. I usually never find a meaning in my dreams. They seem like a product of my imagination and weirdness and false logic.
Other than that, it sounds like a funny dream if that's what you were looking for
