Why are we so incredibly different?

My elder sister and myself. She is 4 yrs my senior. How is it that two people grow up raised by the same good stable caring parents in the same home etc and yet at mid life are on completely different pathways. We speak and get along with each other very well but are more like occasional friends or acquaintances and live in different countries now. I have another sister one year younger than this one (also overseas living just a few miles from the eldest one) and who is my absolute soul mate on a level wavelength in most things. At one point we have all three even had similar careers. But my life has twisted wandered and turned all over the place making for some quite extreme happy sad and often hilarious scenarios.
Is it because I am something of a soldier of fortune whereas my eldest sister has probably never even had a red overdue energy bill and leads what appears a very mundane "married" life.
What makes these distinctions between family members as they reach mid life ?