Disclaimer: FMA is a brilliant manga and anime, that I didn't indulge in until after even the movie was out and old.
Dear Father,
Alphonse paused, the tip of his pen suspended over the smooth surface of his paper. What was he to say?
What was he to write?
What was he to ask?
What was there to say at all?
Was there anything to say?
Anything to say---other than this:
Alphonse put his pen to the paper again, writing with small, hesitant scratches of point to surface.
How are you? Where are you now? I hope you're coming home soon. Mom misses you, you know. She thinks about you every day, even though she doesn't let it show. She's strong, she's always cheerful and smiling, raising Brother and me. But I've seen her looking to the distance whenever she thinks no one is looking. She looks with a faraway look in her eyes, and even sighs. She misses you. So come back soon.
Brother is---
Alphonse paused again, lifting his pen from the cream-hued surface.
Alphonse paused again, mind empty.
Anything else? a voice whispered from the back of his head, and Alphonse's hand twitched. There was so much to say---had Alphonse known Hohenheim better. Where was his father? Why did the man leave? Why?---why did he leave?---why did he leave his wife and sons?
There was so much to say, and so much to hide.
Questions rushed through the young boy's head: Why did you leave? Are you coming back soon?---when are you returning? Do you miss Brother, Mom, and me?
News: Brother didn't drink milk again. I think he might be secretly allergic, but it seems that he just hates it. He caught a rabbit today, but let it go. Mom loves our alchemy---
A demand: Come home.
A slight prickling feeling crept up Alphonse's body, and he closed his eyes. So much to say---so much to keep.
He picked up the paper and crumpled it, making a mental note to toss it into the fireplace as soon as he could.
He picked up another sheet of paper, brain sparking with thoughts. None of them seemed right.
Dear Father, he wrote; a bead of sweat appeared upon his brow and trickled down his face,
Come home. Mom misses you. Brother and I are learning alchemy, and she really likes it. Come home, please. I want to know you. Why did you leave?
Alphonse shook his head, as the movement of his pen paused again.
What was he to say?---to this legend of a man, a father who was less than a stranger to him.
Dim memories were the small shreds of Hohenheim, the man who was his father, the one he was supposed to somehow resemble (but more in Edward), in some way.
Fading photographs in the mind, priceless and leaving---a memory of defensive arms that held him close against the wind, security and love, a kindly face before him. A pair of pants that he tugged at, stopping the wearer in his tracks.
Hohenheim. Hohenheim, Father. Father.
Alphonse shook his head at himself, picked up the paper and folded it. He would never send it anyway; what point was there?
He would keep it, for the letter said enough. Short as it was, it explained everything.
--
Edward paused in mid-step as he noticed something in the flames of the fireplace, something that caught his eyes.
Crouching, curious, he saw a bit of crumpled paper, and made out two words---
Dear Father,
The flames ate up the paper greedily.
--
PT: Intended to be short. I didn't want this to drag.