How old is Patrick from Indian in the cupboard?

In "The Indian in the Cupboard" by Lynne Reid Banks, Patrick is depicted as a young boy, around 9 years old. He is the older brother of the protagonist, Omri, and serves as a foil to Omri's character throughout the story. Patrick's age is not explicitly stated, but he is generally portrayed as a child in the same age range as Omri.