Am I being selfish about this?

I have a rocking horse, It was the first present I had on my first christmas, and It has always been special to me. Even now, when I'm 14, can't use it and it's old and tattered, I just can't part with it. Anyway my little sister wants it and I told her no, because it was my first ever christmas present and if any child is going to have it, it will be my eldest child. I told her she can ride, but not own. My parents say it will always be my rocking horse, Is it selfish of me to keep it?