Little boy licking his brothers face

So I'm babysitting two boys one is 7 the other is 2 they are brothers. As I'm sitting here I look over and the 7 year old is licking not just one lick but like a several licks on his brothers face this made me uncomfortable and I told him to stop. Then about 20 mins later he kissed his brother on the mouth just a peck but ik his father would not like this because his father doesn't kiss the 2 year old on the mouth because he doesn't think it's okay. Should I say something about the face licking to the father??? I think that's very strange.