Genetically Programmed to Miss Deadlines?

As an oldest child, I've always wondered, what's the point of setting an a "good example" for younger siblings? Am I really part of their "nurture" component of their personalities? My middle sister and I are completely different. I like science and math, while she likes art and writing. Our attitudes on subjects like financial matters makes it seem like we grew up in two completely different families. My hypothesis is the setting we grew up in. Even though we are only three years apart, most of my formative years were spent in a small house, which she was probably too young to remember. She spent the last part of her formative years in a large house. I wonder if that caused her to be a spender and me to be a saver. Either way, why do I need to be a good example if she's already set in her ways? Even my youngest sister, who happens to be more like me, doesn't seem to be influenced by me much.
This leads me to wonder about the genetics of political views and religion. I share neither of these with my parents, but for the longest time I was associated with their beliefs when I was younger. How can a child be classified under a certain political view or religion when he or she has only been exposed to one in his or her life? For some reason, most people seem to think that political views and religion are genetic and having larger families will result in more voters or adherents. At the same time there's a push recently for children to "be themselves" because each and every one of them is "special." The two ideas seem to be quite at odds with each other. My hypothesis is that these contradictory messages are what is confusing children today. It certainly confused me.
Anyway, the point of my rambling is that I think that surroundings affect children more than parents, who in turn affect children more than siblings do.