My husband and I have four amazing children. I love them with all my heart, but they're normal kids. They bicker and fight and take turns sitting on my last nerve. I'm convinced that sibling rivalry exists in every household on the planet, but it's not as much about sharing DNA as it is about sharing life.
Proximity = Conflict
When you live with another human being (much less share a room with them) conflict is bound to surface. There's no sense hiding your true self because...well–you're stuck sharing toothpaste and genetic code for what seems like the rest of eternity.
Not so with everyone else in your life. You can't pick your family, but you can be in charge of whether or not all the other addicts at Starbucks see your bed-head or your coif du jour.