Father in law and the way he handles the girls

Hi there everyone, I have a father in law that is ruining my life to say the least. Besides his actions, everything that I tell my wife, she ignores and thinks I'm over reacting and basically takes his side. My father in law has five grandchildren. 2 are mine and three are my sister in law's. 3 girls and 2 boys. He constantly grabs the girls every time we are at their house or parties and puts them on his lap, then tells them over and over that he loves them, asked them he they love him, kisses them constantly on the lips, always putting his hands up their tops to rub their backs, smacks them on the ass flat out, even when he picks them up he picks them up by their bum instead of their arms and it's pissing me off so I confronted my wife and like everything else. I'm being silly, or I get her getting angry . " What are you saying, that my dad's a molesterer". I say no but I don't like it and it concerns me that he has some obsession with touching the girls and constantly putting them on his lap. He won't leave them alone. And he's not like that with the 2 boys. He also acts like his their parents and I can't be a parent when he's around because he takes over. Does anyone have any advise?. I feel like the only option is to get a divorce because my wife is on there side and loves her parents to death. Even once I went to pick up my kids from there house and no one was home when suddenly the mother in law came home and I said where's my kids she said there with your father in law out shopping so I responded that from now on if you take my kids somewhere can you let me know. She looked me straight in the face and said No. After arguing with her I left followed by my wife calling me saying that she is on her mum's side and that she doesn't need to ring and let us know. This is only a few of my delemas. Please give advice and thoughts via /r/Parenting https://ift.tt/2pJaOsK