My 14 yr old son does things for me without being asked, more because he adores his little brother like nothing else!
The things I do ask him to do is to entertain Harrison whilst I am cooking/cleaning etc, and to strip Harrison's clothes off him to ready him for a bath at night. James usually chooses outfits for Harrison and Madeleine doesn't mind changing nappies, as long as they aren't pooey ones! lol