I don't think you can.
I think it's something that just happens.
Events that no one can plan or force on them
It happens through sleeping on top of each other in the car.
It happens through eating popcicles on the porch
I think it comes from being allowed to be silly together.
It comes from being allowed to fight with eachother, and learning how to work it out by your self.
I believe it happens when you set an example as parents of what bonding and cooperation looks like.
They don't learn how to communicate unless they see what communication looks like.
You can't force kids to do anything, believe me, I've tried.
I think the trick is allowing you kids to be their own person, and not making them into someone you think they should be.
Kids need to be allowed to make their own decisions (within reason). How are they to know what making a wrong choice feels like, if they aren't allowed to make wrong choices?
Siblings become buddies because, like adults, they have formed a friendship with each other. They have been taught to love and then given the opportunities to show that love, and feel that love from each other.
Siblings form an unbreakable bond from fighting, making up, picking on each other, and sticking up for each other.
There are moments, everyday, when I wonder if they will ever get it. If they will ever form that unbreakable bond.
And then something happens, everyday, when I see that they have.
They stick up for each other, they protect each other, they love each other.
When one is down, the other 2 know, they care, and it makes them sad. It's makes my heart smile and I like to call that "pay day". It's moments like these when I look at my 3 amazing kiddos and realize that no matter what happens down the road when they have grown and gone, they'll be OK because they have each other and they have the unbreakable bond that only siblings can form.
One for all and all for one.