I was the "typical" competitive, aggressive, Type A but not so social older child, my sister more outgoing once she got past teenaged sullen, rebellious stuff. I miss her. I'm now an only child, although I have stepsiblings I'm close to, and it's not fun getting used to that later in life.
And BR is indeed an introvert until she gets to know you. Then you will hear many opinions, all of which are interesting and some of which are fiercely emily samuelson held.