Ever since Elliot learned to crawl and pull up on things, the sibling hostility level has reached new highs. Henry can give his brother a hug and then, moments later, when Elliot pulls up onto the train table, Henry will push him down with an ear-piercing shriek. Most times that Elliot is crawling towards toys, we hear "Aaaaah! Brother! Mama pick up brother!" (yelled with the same ear-piercing shriek). Several times, Henry has stomped on Elliot's hands while Elliot is crawling towards a toy. That is neat.
Needless to say, our timeout chair has gotten a lot of usage lately.