Take a look at a pair of kittens playing together. They hit and bite each other, and what does the mother cat do about it? Absolutely nothing. Why? Because hitting and biting are perfectly natural behaviors for kittens. Toddlers are the same way. They are naturally aggressive, at least up to a point, and attempting to parent all violent behavior out of existence and program Jimmy into a flower-power frame of mind could backfire. How? Well, positive or negative attention reinforces the behavior. This is especially true when kids go through phases where they hit those close to them, whether mommies or little sisters.
From a practical point of view, I recommend that you treat hitting as you would any other inappropriate behavior. If it’s just a little tap, let it go. If it’s a big whack, then treat it as a disciplinary issue. Rather than launching into a long lecture on respect, say “Don’t hit your sister” and put Jimmy in his crib for a couple of minutes. Let him vent his frustration there by crying, thrashing, and doing whatever else he can think of. After a couple of minutes, remove him from the crib and put him down by himself with no extra affection, no lecture, and no demonstration. Don’t look for an apology; Jimmy’s not sorry, and it’s not because he’s evil but because he didn’t mean any harm.
Occasional hitting should disappear within the third year of age. If it doesn’t, I suggest you visit us at our Discipline page.