If I Had a Little Sister

IF I HAD A LITTLE SISTER tells an amusing story about a lonely little boy who is an only child and who yearns for a little sister that he could play with. He fantasizes about how, being the older and wiser of the two, he would teach his little sister various skills. He finally realizes that perhaps the little sister he is yearning for would not be as amenable to his plans as he might wish, and he reaches a crucial decision. Can you guess what that decision is?