Only Children Are Not Great at Sharing

i'm very close to my parents, and they are like my best friends, you know. But on the other hand, it's actually kind of emotionally taxing because my parents are so sacred to me that i put a lot more weight on my relationship with them than some of my peers do. One of the negatives is not learning how to share. Like if i would come to school and i would have a new pack of erasers, and one of my friends would ask me for one, the answer was absolutely not. I really hated sharing growing up. Nowadays, i feel like i've relaxed a lot, but even deep down though, i still get a little bit irritated occasionally.