Actually, I had been trying to figure this out too. Because like you, I notice that even among siblings, they have very different skill sets and characteristics. Self-reflection is one. Some siblings can do it very well, on their own. But others seemed to suffer throughout their lives not being able to self-reflect. If they had gone through the same education and environment, shouldn't all of them pick up the same skill?

In Buddhism, it's believe that there are past lives, and it's used to sometimes explain our innate talent - talent that none in our immediate families have. We've all heard of kids who started painting at four, or playing a concerto on the piano without prior lessons. Weird huh?