Frustration: “Oh My God! SHUT UP!”
Siblings are uniquely situated to annoy each other. By the time they reach adulthood, siblings will have had lots of practice managing their internal emotional reactions as well as responding appropriately to frustration. You can help your kids develop greater frustration tolerance by requiring them to deal appropriately with their frustrating sibling. Do overs are good for this. “Wait, wait, wait. Back up and do that all over again the right way.” (Although, sometimes, it is important to just separate them.)
Conflict resolution: “Oh My God! I’m going to KILL you!”
More than anything else, sibling relationships require kids to learn how to settle an argument. However, it is usually not a good idea to leave them to their own devices. Kids (and humans in general) have a tendency to devolve into the worst forms of social organization (e.g., dictatorships, rebellion, anarchy). Sitting them down and teach them the steps of effective problem solving. Then make them use what they learned. There will be no shortage of opportunities to practice; and they’ll need it.
Leadership and Followership: “Oh My God! Just get out of the way and let me do it.”
Playing together requires brothers and sisters to learn about leadership as well as how to follow another’s lead. Consider taking some time to actually require each sibling to be the boss of a task. Help them learn the difference between leading and bossing. They will also need help learning to be a good follower (which doesn’t mean just going along with someone).
Dealing with jerks: “Oh My God! I HATE you!”
Kids need to learn to deal with the jerks in this world. Fortunately, they will have lots of practice with their sibling. Teach your kids how to respond to and work with jerks by requiring them to deal appropriately with each other. (And, afterwards, be sure the jerk is punished for being a jerk.)
Assertiveness: “Oh My God! Get out now!”
Siblings teach each other how to be assertive (because at least one of them is bossy and overbearing). Encourage your kid to speak up for themselves (though you may have to stand right behind them for moral support). Role play assertive responses. (And, quietly threaten your over bearing kid if they don’t respect their siblings attempts at being assertive.)