Flystock/Shutterstock Siblings often have different personalities, and their places in the birth order may be partially responsible. First-born kids tend to be leaders, like CEOS and founders, and are more likely to achieve traditional success. Middle-born children often embody a mix of the traits of older and younger siblings, and they’re very relationship-focused. Last-born individuals are used to fighting for attention and respect and aren’t afraid to break the rules and redefine success. We tend to associate first-born siblings with leadership and success and “the baby of the family” with rule-breaking and humor.