2 only children

I am the mother of 2 "only children." I swear....both of my kids were meant to be the "only child". They fight incessantly. Today has been especially trying.
Grant is at this age. Numerically speaking, it's FOUR. Emotionally, mentally he is at the age where he transforms from baby to child. Of course, he hasn't been a "baby" for quite a while, but he is now becoming more independent (wiping his own butt, learning to dress himself, think for himself, etc.) He is also testing the waters of discipline. He's proving (or disproving) us.
It's wearing me out.
I remember Brooklyn at four. It was the same thing then. I think four must be "that" age. Have you guys noticed that four is particularly difficult?
What's crazy is, if my kids are alone (meaning not together) they are both SO MUCH MORE enjoyable. EVERY single time we split them up and Matt takes one for the day and I take one for the day, we end up saying how GOOD our kid was. We almost argue about which kid was better! Then we get them together and all you-know-what breaks loose. I know some of you probably think I'm exaggerating, but I assure you...I can't emphasize enough how CONSTANT their bickering really is. Some of you have witnessed it, so you know. Literally, I would say they get along 10% of the time. The other 90% is spent either sleeping, crying or fighting with one another.
I keep thinking that they're gonna get a little bit older and become friends...but I'm beginning to wonder.
We joke sometimes that we ought to move one of them in with my mom and just take turns having each kid. We could get them together for play dates every once in a while. ha ha
On a different note...similar subject: We are raising some terribly ungrateful children, I'm sad to say.
This is just one example: Tonight Matt and I took them to a movie (Nim's Island) and then out to eat at the resturant of their choice, which happened to be the Elephant Bar. They got to order whatever they wanted and lucky for them, their meals came with a hot fudge sundae AND a soft drink---2 things we don't typically buy when we eat out. While we were eating they spotted Toys-R-Us across the street..and from that moment on it was "Can we go to Toys-R-Us?" over and over and over. When we had answered them 15 times each and were starting to get REALLY mad, they started saying how mean we are.
Boy, I wish someone would be so mean to me! ha ha
The other night I took them out to fly a kite-something we very rarely do. Afterwards, I was really ready to go in, but they were begging to play basketball so I said okay. Brooklyn took her shot, then Grant shot, then it was supposed to be my turn...but no---Grant didn't want to let me have the ball so he picked up a rock from our driveway and threw it at me. It hit my ankle bone which hurt like HECK. I got upset and said we were going in--no basketball. Oh boy...for the next half hour I had to hear (from Grant) how I was so mean, how he doesn't like me, how I am not nice, how it's no fair, blah, blah, blah. I know he doesn't understand..but I just wanted to scream at him: I did kites with you! I tried to play basketball with you! I didn't get to even take one shot with the ball and you threw a rock at me! I'm sitting here in pain and YOU'RE the one crying! AUGH!!!!
Anyway, I know that it's gonna be all okay and before long we'll be onto the next speed-bump in life..but for right now...I REALLY want a vacation from short people. 24 hours---I think that'd do. hmmm......