The kids are in the backyard playing in the kiddie pool while the adults are a few feet away bbqing and talking amongst themselves.
Everything is going great until your daughter screams and all of the adults turn their heads to see your nephew trying to jump on your daughters back trying to dunk her under water. His mother yells "junior stop that! Don't hurt your cousin, play nicely!" Junior looks at mom and then turns back to your daughter and jumps on her back again.
Your father sees this and worried about your kid and closer than the other adults gets to them quicker and grabs your nephew up and spanks his wet behind. Nephew cries out and squirms and just as grandpa goes to spank him again he moves and grandpa accidentally hits his back harder than he meant to.
Your sister grabs her son up and stomps through the house and gets in her car and leaves in a huff while your daughter is screaming, scared of not only the water but her cousin as well.
A few hours later your sister texts you a picture of her sons back showing welts and she tells you she's furious at your father for doing that to her son and he will never see his grandson again. She never asks if your daughter is ok.
Meanwhile your daughter has been latched on to you, something that's unusual for her and when your tried giving her a bath she becomes hysterical and tells you she doesn't want to play with her cousin.