Welcome Jen,
You know, people do not surprise me anymore. I do not put it past anyone to do anything anymore either. So you doing what you can to make sure your children are protected is the best thing to do. My jaw dropped when you stated that your Dad said your Sister had been threatening your kids for a year. I could not imagine someone keeping that from me. I am so very sorry. Please keep your chin up, take care of your little ones and try to regain some serenity by staying out of the drama...
Progress not perfection.......MissTara