J.K. Rowling’s published name uses the initials J.K. Her birth name is Joanne Rowling, and the “K” was added at her publisher’s suggestion before the first Harry Potter book appeared.
Rowling has said that she had no middle name at birth. The K was taken from Kathleen, the name of her paternal grandmother. The initials were also considered useful because the publisher wanted a name that would appeal to readers of different genders when the first book was marketed as children’s fiction.
The name is usually written with periods as “J.K. Rowling.” She has also published adult fiction under her own name and crime novels under Robert Galbraith. “Joanne Kathleen Rowling” is therefore a common expansion, but the initials do not represent two original given names recorded on her birth certificate.