I don't have an older brother or sister as I was the eldest of two, and DH is also the oldest, so I don't know what it's like from the younger sibling's point of view, I'm feeling curious tonight!
Did you envy them for being older, able to stay up later, having more independence, getting to do many things before you? Were they protective of you, or did they see you as an annoying little one? Did they babysit you? Was there a lot of "when I was your age...", or "I can't tell you that, you're too little"?