Annoying family member will post on Facebook

My DH's brother has minor learning disabilities so gets away with everything in his family. He's always posting awful pictures of everyone that he takes at family events, and he posts pics of his friends kids without asking them. I'm so terrified that when we tell him about the pregnancy he will post it on Facebook! I am not planning to post anything myself until the 3rd trimester, and I plan to not post many (if any) pictures of my baby when it's born. How can I make sure he doesn't post our news and pictures?? He throws a fit if you tell him he can't do anything.