I guessed with mine too lol I guessed my biggest was a boy because of size but he is a she and that the two smaller were girls. One is for sure a girl the other might be a boy. Size really doesn't matter. Girls can tend to be more outgoing, louder and friendlier with Rouens from what I've heard but honestly idk if that is always true either as are most timid and our most friendly are both girls. Voice sexing is definitely the way to go.