J.R.R. Tolkien and his wife Edith had four children.
Their children were John, Michael, Christopher, and Priscilla. Tolkien married Edith Bratt in 1916, and the family remained an important part of his personal life while he worked as a scholar, university teacher, and author.
Christopher Tolkien later became especially important to the preservation of his father’s literary legacy. He edited and published several posthumous works, including The Silmarillion, Unfinished Tales, and the twelve-volume History of Middle-earth series.
A related family fact is that Tolkien wrote and illustrated annual letters from Father Christmas for his children. These were later collected and published as Letters from Father Christmas. The number four refers to Tolkien’s children with Edith, not to the number of major children’s books he wrote or to the members of any fictional family in Middle-earth.