A Rough Day and a Rough Phase

We've been going through a rough patch lately with Joshua in terms of behavior.  He's mostly struggled with impulse control.  He'll do things he knows are bad, but he has an opportunity to do them and won't stop himself.  The thing that irritates me most is his antagonizing of his sisters.  In my family growing up, my sisters and I had remarkably few fights and squabbles.  I think that's partly due to our personalities, but it's also because of what our parents taught us.  I stress the same tenets that were part of my upbringing: We're all on the same team.  We don't do things that hurt each other, either physically or emotionally.  If we see one of our siblings is sad, we should be sad too and want to know what we can do to help.  We don't want anyone in our family to be sad or mad or frustrated.  But Joshua just gets too much enjoyment out of doing something to frustrate someone, usually Clara, and then when he sees it bothers her, he does it more.  I know this is very common for siblings, but it wasn't how our family was growing up, for the most part, so I'm doing my best to minimize it.  He's been spending a lot of time sitting by the front door in timeout recently, and also in his room, which is the next level of punishment if he doesn't act appropriately when sitting by the door, or if he commits a bigger offense (like hitting or kicking a person or animal) which warrants an immediate sending to his room.  I expect that this is largely a phase, or essentially just part of growing up and learning rules and boundaries and that he'll get better, but it's been a tough thing to deal with.  Today was especially bad, and he even got sent to his room during our group bedtime routine,  which made him cry.  Here you can see the aftermath, as he's been crying but is also tired.  He still takes comfort in his "animal blankie", so you see him here snuggling with it.  Hopefully this situation improves, and I'm pretty sure it will.