thinks he's a quad

After the 'you must have your hands full', 'so you finally got your boy' seems to be one of the most common comments i hear when people find out that i have triplet girls who are 8, and a son who is 6. That really bothers me. We wanted another child, not just a boy.
When we went through our 4th round of IVF, we became pregnant with our daughters, and were also able to freeze embryos. After our daughters were born, i often thought about that, wondering if we really could have another child, or if our family was complete. We didn't want a large age gap, so we decided to go ahead with the transfer as soon as we felt we could handle another child. When the girls were 18 months we went ahead, and became pregnant with our son. We thought this would be our normal pregnancy, and that the girls would be potty trained before he was born. But there were complications with my health, and he was delivered 10 weeks premature. Just 8 days before the girls turned 2.
We enjoy the experience of raising a boy,but in some ways another daughter would have fit in more easily. he doesn't always like the same games that they do. He has found his own way though. When the girls would play barbies, he would push a dump truck along side and offer them a ride. When they would play house, he was usually the dog. Now that they are older, they all play video games together, along with soccer and basketball. A girl could have shared a room with her sister, and worn the handme downs. instead the 3 girls share the larger bedroom, and sometimes they lock him out.
He is not only a boy in a house full of girls, he is also a singleton in a house with triplets. He wasn't pushed so much to hold hands and stay together. He is more curious and likely to wander off. Once the girls started school, He went out more with just one adult. for the girls that one on one time was hard to come by. The girls also have a group of freinds from school that he doesn't know.
There are times that it becomes clear that he is not one of them. usually 2 of the girls sit with a freind on the bus, and the 3rd sits with ray. one day he decided that he wanted to sit in the seat by their freind, upsetting the girls. He sees her as his freind too, even though she is the girls age. This same freind had a birthday party, and he is not invited. he doesn't really understand why he can't go. We tried telling him that it's a girls party, but he doesn't care about those diffrences yet.he just feels left out. We also tried explaining that someday one of the girls would be invited to a party without the others, but none of the kids could grasp that concept. We will deal with that one as it comes, it's just part of growing up.
I asked him what he would like to do while the girls were gone. Grandma stopped by and he played board games with her. And my husband took time to play a wii game with him. i took the girls to the party, and then ran some errands. when i came home with out them, he wanted to know where they were. then every 15 minetes he was asking if it was time to pick them up. he picks on his sisters, and complains about sharing computer time, but he also misses them.
I don't mean to say that we aren't glad to have him. He is creative,and energetic. I think having a brother, encourages the girls to try new things. My husband also enjoys having a son. My point is just that having both sons and daughters shouldn't be assumed as the perfect arrangement. Each family has it's own strengths and tensions.