Passage: Rowling's sister Dianne was born at their home when Rowling was 23 months old. The family moved to the nearby village Winterbourne when Rowling was four. As a child, Rowling often wrote fantasy stories which she frequently read to her sister. Aged nine, Rowling moved to Church Cottage in the Gloucestershire village of Tutshill, close to Chepstow, Wales. When she was a young teenager, her great-aunt gave her a copy of Jessica Mitford's autobiography, Hons and Rebels. Mitford became Rowling's heroine, and Rowling read all of her books.Rowling has said that her teenage years were unhappy. Her home life was complicated by her mother's diagnosis with multiple sclerosis and a strained relationship with her father, with whom she is not on speaking terms. Rowling later said that she based the character of Hermione Granger on herself when she was eleven. Sean Harris, her best friend in the Upper Sixth, owned a turquoise Ford Anglia which she says inspired a flying version that appeared in Harry Potter and the Chamber of Secrets. Like many teenagers, she became interested in pop music, listening to the Clash, the Smiths and Siouxsie Sioux and adopted the look of the latter with back-combed hair and black eyeliner, a look that she would still sport when beginning university.

Question: How old was Rowling when his family moved to Winterbourne?
four