Complex sentence: He is the only son of Dona Paula, Catalina's boyfriend, the little one, by obligation begins to work for La Diabla and becomes the bodyguard of her daughter Daniela.
Split into simpler sentences: He is the only son of Dona Paula, and Catalina "La Pequeña" 's boyfriend. By obligation, he begins to work for La Diabla and becomes the bodyguard of her daughter Daniela.