By constantly modeling respectful good behavior and correcting them when they are rude or mean to each other.

High fences make good neighbors. Most of the really serious conflict between my sister and I was related to competition over use of shared resources like the family computer or TV. Perceived unequal treatment was another big one.

Don’t make them compete for your respect and affection.

Mine fought like banshees when they were young but are so close and friendly as adults. I didn’t do anything to make any of it happen as far as I can tell. I never understood why they fought so much, and they are so funny and love each other so much now.

Strive for equality of treatment.

Growing up my sister and I didn’t get along when we were younger, she wanted to give me back to the hospital when I was born.

Over time we shared some similar interests, she played violin, I played cello. She pursued it to a master’s degree, I quit to have less divide attention on school which I also failed at.

My parents always gave us options for what we wanted to try and despite her getting more financially to cover those things, I knew I could have those things as well if I asked but I wanted them on my own.

By our early teens any anger was over and was got along for the rest of her life when she died of brain cancer at 42.

Love them both for who they are and never compare them.

Make them unite in their hatred for you.