How do three kids with the same parents, living in the same house, develop such distinct personalities? A key reason seems to be birth order. Many experts believe that a child's place in the family is intertwined with the hobbies he chooses, the grades he'll earn in school, and how much money he'll make as an adult. Birth order isn't the only factor that contributes to how a kid turns out, but giving it consideration can help you understand your kids and help them succeed. The firstborn is often used to being the center of attention. "Many parents spend more time reading and explaining things to firstborns. It's not as easy when other kids come into the picture," says Frank Farley, a psychologist at Temple.