All child-rearing books warn about cats becoming jealous. After studying the reactions of our cat, our conclusion is that it is not about jealousy: babies crying sound like fighting cats. So a cat could react aggressively thinking there is an intruder. In our case, Choclet is a scaredy cat and so just runs away the moment he cries. He's now beginning to get used to Julian. (Don't worry, we never leave them alone together in a room.) 
