three.
As a soft, round baby, Ron was perfectly harmless.
Until the age of two, he slept in his parent's room in a small cradle, which had previously been used by each of the Weasley brothers. Except Percy. Percy had had his own cradle. That was sold to a family friend from the ministry when Percy turned three. The money was eventually used to buy Bill's school robes.
Each night, when Molly put her small son to bed, Ron would sing himself to sleep. He would sing songs he heard from his brothers, or the odd enchanted object that hummed to himself. He heard his great-great-great grandfather Weasley hum odd out-of-tune melodies from his portrait in the living room, sometimes. But mostly the little mind of Ron's came up with his own tunes to sing. Molly and Arthur would also fall asleep, listening to their baby boy humming off-key to himself.
Before Ron turned three, he was moved out of his cradle in his mum and dad's room, replace by his younger sister, Virginia Weasley.
Ronald shared a room with two of his brothers, Fred and George. The first night Ron slept there, he hummed a comforting tune to himself.
The second night, when Ron started to hum, Fred told him to shut up. George told him he was being a git, keeping them awake and all.
That was the last of Ron's quiet concerts.
A few years later, when Ron turned six, He was given his own room. It was a small room, at the tope of the house. Fifth landing near the attic. It would eventually be covered entirely in Quidditch posters of the Chudley Cannons.
And never, ever, would Ron sing to himself again.