Complex sentence: He asks Marge to buy it, but she refuses, at bedtime she tries to tuck him in while singing a lullaby, but Bart explains that he is too old for babying but Marge doesn't listen.
Split into simpler sentences: He asks Marge to buy it, but she refuses. At bedtime she tries to tuck him in while singing a lullaby, but Bart explains that he is too old for babying, but Marge doesn't listen.