My BIL thinks that the mother is primarily in charge of the kids, I think, and doesn't really interfere much.
When my nephew was younger (maybe 2 or 3) he came out of their bedroom holding a stick of my BIL's deodorant. He looked like he was going to take a bite out of it for some reason, and my SIL shrieked "DS! If you eat that you'll have to go to the doctor and get shots!" And then wonders why she has to drag them kicking and screaming for their checkups...because she has made them bloody terrified of the doctor, that's why!
Anyway, BIL looked at her askance but said nothing. He really never does. And he's a "macho" type of guy and he makes fun of my nephew for being afraid of everything, which isn't fair because he doesn't say anything when SIL is instilling these daft fears into my nephew's head.
They rarely come over to our house, but when they do I always encourage them to pet our dog or throw the ball for him. (He's a very big golden retriever mix, but gentle as they come) Sometimes they will. But once when they were leaving my niece and nephew were having tantrums because they didn't want to go and my SIL said "oh, the dog's going to get out and chase you!"
No, he damn well will not! I just said "Oh, no, he love kids. He might lick you, but that's it! Now come on, it's time to go but come back soon!"
And at DS' last birthday party it was boiling hot and I told her to bring the DC's swimsuits so they could play on the slip 'n' slide and in the pool. She didn't. When she got here she said "Oh, they don't like cold water." (I think she thinks cold water will make them sick
) I took her aside and said I could find shorts for the DC to swim in, it would be no problem, but she just said "oh, they'll get cold and whiny, they won't like it, etc, etc" Meanwhile DS was having the time of his life leaping around in the water and her DCs were begging her to let them go in. She kept telling them that DS looked cold, and was "dirty, see, he has grass on his face, that doesn't look like fun!" but of course it did, it was 37 degrees out! Finally BIL said "just let them go in". She protested but then finally did. They had a ball.
Sorry, I know this is long and sounds really petty, but I feel like I am going to explode if I have to sit through another family gathering anytime soon!