How do I deal with how much my older cousins have changed over the past few years?

Ok. So I saw my older cousins for the first time in a while back in December. They are out of college but still somewhere in their 20's and I am 12. Back then I was 11. They are both boys and I am a girl. I was so exited to see them that I didn't think I could stand the wait. They had always been basically my favorite cousins. I hadn't seen them in at least a year since they live in different states now. I spent so much time picking out what to wear and how to do my hair. I was a little bummed since one of them was bringing his girlfriend but I could deal. I knew they would have changed some but when I got there it was much more than I expected. My personal favorite of my 2 cousins (also the older one) was the one not bringing a girlfriend and the one I was most exited to see. He always payed a ton of attention to me, almost more than the adults. The other cousin payed a ton of attention to me too, but not quite as much. I could imaging the exact words my favorite cousin, Ben would use when he saw me, "Hey Swan!". Swan had always been his nickname for me. It was a special connection that we had. I never understood it but I knew that it would be my nickname forever, and I loved it. But when I got there he surprised me with a hi and using my full name. No nickname. Plus instead of a big bear hug like normal he offered me a simple handshake. From there the only thing like old times was a wasabi eating contest with Ben and I. I didn't blame my other cousin Dan quite as much since he shunned everyone exept his girlfriend unless they were talking to him about the house the two of them were planning on buying. But Ben basically ignored me exepet the wasabi eating contest. We used to almost have to be seperated at the table because we would knock the whole thing over with our games. Now we were hardly even talking. He only talked to the adults. I just stood in the corner for most of the get together. My mom says that it's just because they're young adults now and I realize that but I really miss the old Ben and Dan. We might see them again soon and I don't know what to do. I just want them to be their old selves with me. It seems like the only older cousins I had that acnowledged me and almost treated me like an equal were taken away and it was like my other older cousins. I was the cute little girl that everyone thought was cute but didn't understand anything. I kinda want to be mad but I know that I'm really just hurt. I want them to know that they aren't the only ones that matured and that I did too, but I wish they realized that didn't make it so that it couldn't be like old times. I'm really sorry that this was so long and thank you sooooo much for helping. ^_^