Which Tolkien family member edited and prepared The Silmarillion for publication after Tolkien’s death?

Christopher Tolkien edited and prepared The Silmarillion for publication after J.R.R. Tolkien’s death.

The Silmarillion was published in 1977, four years after Tolkien died. It is a collection of mythological and historical narratives describing the creation of Tolkien’s world, the Valar, the first age, the Silmarils, and the histories of Elves and Men.

Christopher Tolkien had worked closely with his father and became the principal editor of Tolkien’s unpublished writings. He selected, organized, and sometimes reconciled versions of stories that Tolkien had developed and revised over many decades. Guy Gavriel Kay assisted with the editorial work on the published volume.

The book is not a conventional sequel to The Lord of the Rings. It is closer to a mythology and history of Middle-earth, and its structure reflects the unfinished state of much of Tolkien’s legendarium. Christopher later edited many additional volumes in The History of Middle-earth series.