C.W.
Hi J.
thank you for taking the time and energy to "save" your brother. It is always a difficult situation when you try to blend families- and your case is no different. It looks like your brother is trying to "make his place" with the two younger ones and is in desperate need of love and affection. Family discussions on behavior wouldl help. Let him know his behavior is not appreciated but that you still love him and want him to be a part of the family. also, be sure your children do not take the back seat to your brother. If after a little while of family discussions and careful watching of the three, you do not see a difference I would suggest some professional help.
There are agencies out there that can provide this for you at little or no cost.
Thanks again for coming to the rescue of your brother.
Good luck and blessings