Parenting styles

I have a 5 year old and am living at home with my parents til my husband and I finish building our house. My parents adopted two kids who are 4 and 5. Their parenting methods are sometimes a head scratcher, but I respect that that's their own way. I stay out of it. My step dad uses scare tactics to make their kids listen. For example, we live in the middle of woods and there are absolutely NO BEARS and my step dad tells them if they don't listen the bears are going to eat them. If they go into certain rooms monsters are going to take them. This is starting to affect my son. He's scared to go around bushes because he thinks bears are going to get them and same as monsters! It's really frustrating! I've talked to my parents about this and they've "stopped" but it's engraved in the kids heads. I've explained to them that it's impossible for bears to be in our woods (we live in S.E texas) and monsters are not real but the 5 year old still talks about it if me or my son get close to the woods or certain rooms in the house. I've also tried explaining real life concerns and that is a reason to stay away from the woods and rooms. what else can I do?