We're learning how important it is both to preserve sibling relationships if they work and repair them if they're broken. We're also learning a lot about nonliteral siblings - stepsiblings, half-siblings - and the surprising power they can have.

It's one of the worst-kept secrets of family life that all parents have a preferred son or daughter, and the rules for acknowledging it are the same everywhere: The favored kids recognize their status and keep quiet about it - the better to preserve the good thing they've got going and to keep their siblings off their back.

Certainly, people can get along without siblings. Single children do, and there are people who have irreparably estranged relationships with their siblings who live full and satisfying lives, but to have siblings and not make the most of that resource is squandering one of the greatest interpersonal resources you'll ever have.

Habitual texters may not only cheat their existing relationships, they can also limit their ability to form future ones since they don't get to practice the art of interpreting nonverbal visual cues.

If you're an older sibling and you have a younger sibling who needs mentoring or is afraid of the dark, you develop nurturing and empathic skills that you wouldn't otherwise have.

All behavioral or mood disorders - including depression, OCD, ADHD and addiction - have some neurochemical components, but sufferers can still work to overcome them.