I guess I never noticed sibling violence as much growing up, since I was an only child. And now I see it everywhere. Last night I watched some kids during a speaking event hosted at our church, and I had a couple of brothers, ages 5 and 3, who enjoyed tackling and sacking each other. Big football fans, that family.
And my own sweet pair have been providing non-stop wrestling action in our den the last few weeks. I've had to scold Two on numerous occasions about pulling Big Girl's hair, and remind Big Girl not to be too rough when she pins her brother and sits on him. They're pretty evenly matched. He's shorter but the same weight, pretty much, and he's good at getting her off balance and dragging her down. She's a little more agile and can dance around him with increased coordination. He has figured out how to use her long hair and her dresses to his advantage, while she knows just how to pin and tickle him, because he is incredibly ticklish.
I stay out of it unless they get too rough or threaten to break or damage anything, and if they accidentally hurt each other, they're both quick to hug and kiss the other and apologize. It's really cute when they hug. I need to get a video of this so I can embarrass them with the footage in front of their prom dates some day.