To my sister Julia, who will do great things...

We never had planned this
We never tried.
You're a siter, my sister,
And I still ask why.

All the fighting and noise
And pulling hair;
You're a sister, my sister,
And it's just not fair.

We're sisters, and sometimes
I regret it.
Yet because of you, I'll
Never forget it!

BUT...

Through our ups and downs
This much is true:
You're a sister, my sister,
And I still love you.

Mary Cieslak

http://www.poemhunter.com/poem/you-re-a-sister-my-sister/