DS2 (2.3) has become quite aggressive over the last couple of months but not in a malicious way iyswim.
He doesn't hit out and bite when he is annoyed/frustrated/when I have said no about something (he just has petulant tantrums then
) but he does bite and hit when he is in a giddy mood - and it is, more often than not, directed at DS1 (4.7) who, to his credit, doesn't hit/bite back thankfully.
Not sure how to handle it - have tried removing him from the room and sitting him on the stairs until he has calmed down but he just thinks this is a big joke and comes back in saying he is ready to say sorry, says sorry and then starts giggling and does it again and then comes over to me saying 'go on the step now' and cheerfully walks to the stairs 
Nursery have never mentioned this behaviour to me so I assume he doesn't do it there and it does just seem to be with his brother (although maybe me and DH pick up on the signs and try and stop him before he gets to that point?).
Any suggestions?