What was the name of J.R.R. Tolkien’s youngest son, who edited The Silmarillion after Tolkien’s death?

J.R.R. Tolkien’s youngest son who edited The Silmarillion was Christopher Tolkien.

Christopher Tolkien was born in 1924 and became the principal editor of his father’s unfinished writings. After J.R.R. Tolkien died in 1973, Christopher organized extensive notes, drafts, and variant texts into The Silmarillion, published in 1977. The book presents the mythology of Arda, including the creation of the world, the history of the Valar, and the wars of the First Age.

Christopher’s editorial work was not simple transcription. Tolkien had left many versions of stories, some incomplete or contradictory, so Christopher selected, arranged, and sometimes connected material to create a readable volume. He later published many additional texts in The History of Middle-earth series.

The Silmarillion is therefore a posthumous editorial work, although its underlying stories were developed by Tolkien over decades.