My issue with my in-laws is my MIL just acts stupid. It's all an act though. She couldn't figure out how to build legos. Who can't build legos? I normally let it go and ignore it but now it's starting to effect my kids.
She was watching the kids when I had the baby and asked if she could get McDonald's for the kids, we told her exactly what to get since DD has life threatening allergies and milk is huge. We told her flat out no French fries only apples because their fries have dairy. As she walked out the door to go straight to McDonald's we reminded her no fries. Guess what she gave DD? And then asked why DDs face was red and covered in a rash. And now she says well she can have fries because I gave them to her once. Uh no.
FIL just thinks he's always right and complains about everything. I ignore him and it's not too bad.