answer:If you’re open to an opinion, here’s mine: this sounds to me like a matter that ought to be left to his parents. If his behavior actually needs to change, let them take the lead on it. It isn’t up to you to push him to take such growth steps unless you’re his primary caregiver. I remember fretting about something a bit similar when one of mine was that age. The pediatrician said, “Do you think he’s still going to be doing that when he goes to college?” “Of course not,” I said. “Well, then, sometime between now and then, he’s going to stop. Let him do it in his own time.” Two is really not so old. If his parents are fine with letting him have a bottle, I’d say don’t worry about it.