How does dominance work in cats? We have a brother and sister. When they moved in with us the girl was v skinny and malnourished. The boy was much bigger (nearly twice the weight). She has gained a fair bit of weight but still considerably lighter than him. He generally initiates play fighting but she always seems to win when they wrestle and he slinks off. They never hurt each other it just seems to be play. We had them spayed and neutered about 6 weeks ago. She has always been the more confident one with us. She likes being at home, he climbs trees but she doesn't want to, she just wants to sleep on someone's lap. If not weight or physical fitness, as he seems stronger and fitter, then how do they work out who is dominant?