punishment

Just explain to him that his being too playful hurts his brother somehow. Show him how he should go about playing with his brother. Be around as they play, and cut him as soon as he goes beyond the limit. He will slowly get within his brother's tolerable levels at play. Ask the older son to try to adjust to the younger son, too. It will always be easier if both of them make adjustments in order to have a more desirable level of relationship developing of between them. If you cannot cope with this now, there is a possibility that enmity shall arise between them and you will find it very exhausting, depressing and exasperating.