The record was verified when the book sold 1,000 copies, GWR said.
AlMheiri, whose book is about kindness and friendship, said he was inspired by his sister, AlDhabi, who holds the Guinness World Records title for youngest person to publish a bilingual book (female) and youngest person to publish a bilingual book series (female).
"I love my sister so much and I enjoy playing with her all the time," the younger brother told GWR. "We read, write, draw and do so many activities together. I wrote my book [inspired by her] as I felt that I could have my own book too."