I love this story. It is a pure FMA classic, originally seen in Cheap School, in Dante and Envy's appearance. That scene has been deleted.
Hohenheim is walking. Very bored.
"Hohenheim!" a voice rings out. Dante. "I have an answer! Let's get married!"
Hohenheim stopped in his steps, and went backwards, stowing Dante in his arms. "Perfect," he murmured. "I'll look forward to a child," he told himself.
Hohenheim and Dante have a child. A girl.
"What is the gender?" Hohenheim asked again.
"A girl. I know, this is so worrisome. It doesn't look like me, it looks like you, my dear. If they find out, we'll be arrested!" For if a child did not look like the parent with the same gender, the parents were to be jailed, then fed on bread and water for a year, then whipped to death. If they were still alive, they would be forced to take history lessons for the rest of their lives.
Hohenheim smiled. "I got an idea!"
"Yes?"
"Let's disguise it as a boy!"
"Good! Now, let's prepare a lie when the authorities come around!"
At the moment, an official came in. "Gender?"
"Boy. Isn't he lovely?" Dante cooed.
"Yes." The official held out a piece of paper, a certificate. "This paper states that you, Van Hohenheim and Dante None-Given, are entrusted a child. You are forced to raise this child up. If it dies, you will have to pay a lot of money. If it survives, you will still have to raise it up. It doesn't matter if you don't want to."
The child survived to THREE YEARS OLD. But before that, it was said to be the most adorable little thing born, clear of the male sins of over-domination and lust. (You know why.) On its second Mother's Day, it made a little card for its mother, a work of artistic genius.
"Mommy! I have a card for you!"
"Aww!"
From that day on, Dante would say it was the last Mother's Day she ever got. The next year, there was plague, and Hohenheim was checking his temperature with a thermometer, when the boy/girl walked in. It saw the thermometer.
"Daddy, can I eat that?" it asked.
Hohenheim looked up dazedly. "What? Oh, yeah. Go ahead." He gave the tube to the child.
A few months later, the child was dead. After its parents buried it, they began to talk.
"The money, Hohenheim!" Dante reminded her partner. "I don't want to pay it!"
"Me neither. I have an idea. Let's revive the child!" Hohenheim smiled. "C'mon, get ready to go to the beach. I'll prepare the ingredients."
It was a pure failure. Instead of a lovely innocent cherub who had been torn in between its own gender, Hohenheim and Dante found on their hands a heartless and over-carefree shapeshifter, named ENVY.
I hope that you, like me, endorse this tale of Envy's birth.