Ron had never been as brave as his brothers.
Or perhaps he'd been more brave than they were, and that was the problem. Throughout his childhood, the antics of his older siblings had continued to put him in positions that terrified him immensely and, more often than not, were really quite dangerous. They were always goading him to do things he didn't want to do, or was afraid to do, especially the twins. He was encouraged (or pressured) into doing everything, from de-gnoming the garden alone, when he was six, to standing up on Charlie's old broomstick when it was twenty feet up in the air and vibrating so much it rattled his teeth.
It had always distressed Ron somewhat that his brothers seemed to do such things with effortless bravery, while just the thought of doing them himself made his stomach feel full of stones. But he didn't want the older boys to think he was a coward, so he bit his tongue and did it anyway. Everyone else in the family had been sorted into Gryffindor at school - the house most noted for its bravery and strength of will. Ron was determined to follow in his brothers' footsteps and be a Gryffindor as well, whether by strength of character or sheer bloody-mindedness.
Once, when he was eight, his brothers were playing a game the twins had invented. It wasn't much of a game, really, as all it entailed was climbing onto the highest part of the house and jumping off, but Ron was enthusiastic about joining in. The older boys had been wary of letting their youngest brother jump off the roof, but Fred and George convinced them it was perfectly safe - part of the game involved those boys who were on the ground (namely Bill or Charlie, who had the most experience) casting a Wingardium Leviosa charm and safely levitating the leaper to safety. Ron was desperate to prove himself to his older brothers, so he'd begged and pleaded and wheedled until finally they gave in. Fred and George had showed him where to climb up, and he'd soon found himself atop the highest gable of the Burrow.
Once he was there, however, jumping off had no longer seemed like such a brilliant idea.
He'd stood up there at the top of the house, faded hand-me-down jeans that had once been Percy's flapping around his skinny ankles, and the sleeves of his jumper - which mum had knitted several sizes too big by mistake - rolled up over his bony wrists, feeling very small and very, very high up. The other boys had been yelling encouragement from the grass, what seemed like miles below, waving their arms and jumping up and down as they squinted into the sunlight. Ron stood completely still and squinted back at them; an awkward, gangly shape silhouetted against the sky. He had stood so still and so tense that soon his legs began to shake, and he'd had to bend forward, gripping the edge of a window for support.
The twins had rolled their eyes and announced that he was too scared. That he was too little to have gone up there in the first place. They turned away with identical expressions of scorn, and while the others had been more sympathetic, it seemed a general consensus that Ron was too young, or not brave enough, to jump the way his brothers had. One by one, the other boys had turned their backs and walked away to do something else, leaving their littlest brother standing at the top of the house, feeling small and foolish and desperate, utterly desperate not to look like a coward.
It was definitely too much bravery that was the problem. Because, while his brothers didn't seem to feel any fear, nine-year-old Ron had felt the mind numbing terror in every inch of his body, and he'd jumped anyway.
Of course, without his brothers, there had been no one there to implement the Wingardium Leviosa charm that would have levitated him gently to earth. He'd broken his leg and fractured his right arm in three places.
The other boys had felt dreadful about it for weeks afterwards, even when the injuries were magically healed, and their mother had been quick to admonish them for letting their little brother do something so stupid. She'd also called Ron an idiot, and scolded him severely for being so reckless.
But Ginny, who was eight at the time, had looked at him with admiration in her eyes and told him in hushed tones that she thought he was the bravest person who ever lived.
And when he started at Hogwarts two years later, he was sorted into Gryffindor straight away. Because bravery isn't about being fearless, it's about idiocy, recklessness and sheer bloody-mindedness. It's about being so afraid of something that you think you might burst from it, but biting your tongue and doing it anyway.
And Ron was always too brave for his own good.