Sam can frequently get annoyed by Lydia's curiosity, especially with his toys. But the other day I learned a trick that helped him deal a little better. As I went upstairs to vacuum, I gave him an important mission: "Mama will be upstairs for a few minutes. You are in charge of making sure Lydia is happy. Do you think you can do that for me?" He totally stepped up to the resposibility. I caught him tickling her gently to make her giggle, giving her toys, and even trying to put the gate up at the stairs so she wouldn't be in danger. Maybe instead of telling him "don't tease/yell/blah blah blah" I just need to give him a responsibility to fill. Like father, like son, I guess.