I want a new brother

With my two boys one never knows what to expect in terms of how they will treat one another. Again, I'm not going to sugar coat it, I spend 90% of my time putting out fires between them but sometimes they are really nice to each other. I remember fighting with my sister and how much she got on my nerves (but I love ya now, Kim!) but there was a difference I have noticed between sisters who fight and brothers who fight and it starts with the letter "P" and No, it's not penis, it's PHYSICAL! Tonight, we took a walk to the beach and Jay picked his brother up, wrapped his arms around his waist and threw him into the water. Nick, who didn't mind getting wet, but wanted to do it his own way, started crying which always prompts Jay to call him a baby which makes Nick cry even more. See the domino effect I deal with day in and day out? At that point I end our time at the beach and we start walking home. Nick stopped crying and his hurt feelings turn into rage. He turned his tear streaked face to mine and tells me, "Mom, I want a new brother, Jay is mean." On the other hand, on Nick's birthday Jay was so disgustingly nice to his brother I thought at any moment someone would jump out and tell me I was on America's Funniest Home Videos. Jay and Nick have their moments and when they are nice to each other I try to praise them, especially Jay. Jay is usually quick to help his brother out and when I need something done for Nick at school (taking treats in, returning a library book, bringing in a large show and tell) Jay happily takes care of whatever request/need I have for Nick which I appreciate.
I hope one day Jay will appreciate Nick's extroverted nature and Nick will appreciate Jay's introverted nature. Differences between siblings is what makes the relationships so interesting. In some ways, I am Jay and Kim is Nick and no one can quite make me laugh like Kim!