Ds has recently started licking his little sister (15 weeks), now i suppose in the grand scheme of things it's not too bad - better than the biting phase he went through a few months back - but I'm wondering if it's normal, or if he's being aggressive in a way he knows he won't get told off for? I just find it really irritating but don't want to make a big deal about it cause then he'll just do it more!