Well, all families are different, and within families, each member is different. Even in large families, not everyone has the same type of personality or tastes or interests. It's quite common - in families of any and every size - for some siblings to be very talkative and outgoing and for others to be quiet and shy.In fact, sometimes in a generally boisterous family, some will end up being quiet simply because, with so many talkers competing for attention, they cannot get a word in edgewise!

In many cases, quietness/talkativeness, introverted/extroverted, etc are just natuaral personality traits, and not the result of environment, as was once thought.