Disclaimer: Dolores Umbridge belongs to JK Rowling, not to me. However, the rest of her family and the idea to this story is mine.
I tried to make a halfway sympathetic Young!Umbridge and give her some sort of motivation for being such a *****, other than being totally off her rocker, of course.
Lores had been having one bad day.
Her brother, William, had disappeared. Mother was nearly sick with worry, and Father was angry. It wasn't good, Father being angry.
When Father was angry, he did bad things.
Once, when she'd brought in a kitten for her and Will, he'd drowned it. She hadn't known he didn't like cats. She liked kitty-cats, a lot. The strays in the village were always there to hear her when she had problems, just like her mother's porcelaine collection. She couldn't talk to Will. He was too much of a child, still, and she had to protect him, he was the only member of her family she actually cared about.
She was afraid of Father, and Mother never took any interest in her. She'd given up on them long ago. They didn't like Will too much, either, but normally, she protected him.
She was sitting on the balcony, crouching in a corner, where no one could see her, but where she could see what had happened.
There were Muggles living in the village. Father didn't like Muggles, and she didn't like them either. It was one thing she could agree on with him. One of them children, they had hurt Will, they had thrown stones at him, because his magic had acted up. They had also thrown stones at her, but it didn't matter to her. It only mattered that they'd hurt Will. No one hurt Will. Not her little brother.
She was praying that they would find him. Mother and that women from next door, Diggle, was standing at the door. Father and some of the neighbours were still searching.
Mrs. Diggle said something. "Yesterday, you know, there was a full moon..."
"Hush, don't say that."
Full moon, that meant werewolves, Lores knew.
Then, she spotted the men coming towards the house. They were carrying something.
When they came close, she recognized it, and her stomach churned. She'd thrown up, if she could. She didn't want to see that. Will had to be alright, he simply had to.
They couldn't be carrying his bloody, torn and mangled corpse, they just couldn't.
Mother and Mrs. Diggle came to see them.
"What happened, August?"
"Werewolves." Father's voice was quivering.
Lores felt a swill of hatred coming up. They'd killed her brother, those werewolves. Well, she'd make them pay, those... half-breeds.
She ran inside, and they never talked about William, never again. If they had, maybe she'd acted a little differently, and it probably would have changed a lot of lives.
One day later, a very much alive and bitten William Umbridge was left alone, in a wood, trying to make his way through the world. The boy survived, and wondered why his sister hated him so that she had to be at the very head of the anti-Werewolf legislation.