The relationship differs for each family, depending on the personalities of the brother and sister. I have an older brother and he really isn’t that protective. But frankly, I like to think I don’t need protecting :P. He knows I can pretty much take care of myself. We share a similar sense of humor (sarcastic) and both like to argue ceaselessly about all things so that’s always fun. I think we have a rather cynical view of the world which is good and bad at the same time. Our relationship lacks the “life is good, let’s look @ the birds/bees/rainbows” factor, in a way but that’s how we like it.
On the other hand, my friend and her older brother share the kind of relationship you are talking about. They txt each other and talk daily, they always say “i love you” and are really involved in each others lives. She was getting a belly piercing and he was very mad about it and against it.
Don’t get me wrong, my brother has shades of protectiveness, I just don’t encourage it. He always warns me if i am going the wrong path and tries to talk sense into me, sometimes I listen, other times I mess up and learn from my mistakes :)
I don’t have a sister and always wonder what that would be like.