Luna hopped around Celestia as the sun princess read a letter from her student. The moon princess was unreasonably gleeful that she had apparently found a "kindred spirit".
"He's basically me, Tia!" she explained loudly, a touch of the Royal Canterlot voice creeping into her explanation. "I believe he is me from another universe. But he understands, Tia! He knows what it's like to be evil, then good, then have everyone misunderstand you because you're 1000 years displaced. I don't need to explain anything to him. And the best part, he understands what I'm talking about when I talk of things that happened 1000 years ago, and I don't have to worry about making him confused!"
Celestia sighed. It was good to see her sister this happy. Luna very rarely found somepony she could connect with, and when she did, it was always a sight to see. But at the same time, Celestia had to fight back some less than friendly feelings. Artemis, the name of the alternate Luna that had landed in Equestria, was a very nice stallion. But, as a pony of the night himself, he was spending far more time with Luna than Celestia ever got to. After Luna's return, Celestia had been delighted to be able to have her sister back with her, to spend time with her catching up and rebuilding their close sisterly bond. Celestia had spent more than one night awake, just to keep her sister company. She wasn't going to let what had happened 1000 years ago happen ever again. Loneliness was hard to bear, and all though in the modern Equestria, ponies spent more time out at night, Celestia wanted Luna to feel loved and included.
"...and then we discussed the stars, so lovely! Did you know that in his universe they have the same constellations? Isn't that fascinating, sister?"
Snapped back from her musing by her sister's story, Celestia nodded, hoping Luna wouldn't pick up on the bitterness there. Of course, her hyper sensitive sister picked up on it immediately.
"Is something wrong Tia? You seem...uncomfortable."
"I'm quite alright, Luna, just..tired. I should go to bed. Good night little sister!" Celestia quickly ran to her room, ignoring Luna's confused expression.
I feel like such a child! But it's just not fair! I'm her sister for pony's sake! We are both sisters and friends. I had to do some terrible things to her, but we both know it was necessary. So why is she spending all of her time with this Artemis character? I'm her best friend!
Voices outside her window stopped her. It was her sister and Artemis.
"You're really my best friend, Arty! Nothing romantic, of course, just friends."
"You are my best friend too, Luna."
Celestia felt like a knife and been stabbed into her heart. She wasn't Luna's best friend...this other version of Luna was Luna's best friend. A brother. Luna had always wanted a brother, as she often found it easier to connect with stallions than with mares. Celestia was now officially second place. Angry, the sun princess lost her usual regal demeanor and stormed outside to where the two night ponies were talking.
"LUNA!" she bellowed "I am tired of being ignored! Isn't this what upset YOU all those years ago? Here I am trying to spend time with you and all you want to do is talk to yourself from another world! I'm your SISTER Luna! How could you?" at this Celestia broke down. Tears sprang to her eyes. The only pony who could ever do this to her was her sister, and now her sister didn't wish to spend time with her.
Suddenly, Celestia felt a hoof on her back. It was Luna.
"Sister, Tia...you'll always be my sister, no matter what. Why...I could banish you to the sun and you'd still be my sister." Luna winked. Celestia gave a tiny smile. "Arty is my friend. Were not you always the one to encourage friendship? Sister...I believe you may be, well...jealous."
Celestia stared at her sister. Jealous? But she was ruler of Equestria and semi-immortal. She couldn't get jealous...then she thought of the awful awful feelings she'd felt when Luna was talking about Artemis. Yes...she was jealous. She didn't know how she'd been so foolish.
"Luna...you are right. I am jealous. When you came home, I was hoping for so much time together, but our respective duties pulled us away from one another. Now I realize that I just have to make time for you and visa versa. We'll still be sisters and we'll still be friends, no matter what other friends come into our lives. Best sister friends forever, little sister?"
"Best sister friends forever, Tia. You know...it seems YOU have learned an important lesson about friendship, big sister."
"I...I suppose I have. But I obviously cannot write to myself!"
"I have an idea, Tia."
***
Twilight Sparkle sat in the library, studying away at an ancient spell created by Starswirl the Bearded. Spike was napping in the corner, when suddenly he woke up, belching green flames. A letter appeared in his claw.
"Twilight! I have a letter from the princess!"
"Oh? Let me see!" Twilight took the letter from Spike with her magic, then opened it to read.
Dear Twilight Sparkle, my most faithful student,
Today, I learned a very important lesson about friendship and sisterhood. It doesn't matter who else comes into your sister's life, having a sister is a gift, and she will always be your best friend. Getting jealous doesn't solve anything and only leads to bitterness and disappointment. Instead, make time in your life for ALL of the ponies that matter, and let your friends (or sisters) be happy when they find somepony else to spend time with.
Your Teacher and friend,
Princess Celestia
Twilight stared at the letter. How odd!! Celestia herself had learned a lesson about friendship!
"I guess that just goes to show you that no matter how old we get, we never stop learning...wait..SPIKE!!!!"
"Yes Twilight?"
"Take a letter. This letter has taught me an important lesson about friendship by telling me about an important lesson about friendship!"
Spike made a face. "Yo dawg, I heard you like friendship lessons..."
Twilight giggled. "Oh Spike, stop fooling around and write the letter"
Spike sighed. "Yes ma'am"
"Dear Princess Celestia,
Today, I received a letter from you that taught an important lesson about being sisters and not being jealous. I learned another valuable lesson from that letter. No matter how old you get. No matter how many years you have to your name, you never stop learning. One can never end their studies on friendship, it is a science that can last your entire life.
Your faithful student,
Twilight Sparkle"
"Uh...Twilight? Are you sure the princess won't get mad that you called her old?"
"I didn't call her old..."
"No matter how old you get?' Are you sure?"
"Just send the letter!"
"Ok..." Spike inhaled and sent the letter through his flames.
***
Celestia read her student's response whilst Luna read over her shoulder.
"Did she just call me old?"
