William Blake II is described by Philip José Farmer in Doc Savage: His Apocalyptic Life. Blake was a liar and all-round dastard, who claimed to be the brother of Sexton Blake and a grandson of the poet William Blake through a hitherto-unknown illegitimate son. Farmer identified William's mother as Jill Fagin, and argued that William was more likely a descendent of coachman Arthur Blake than the writer.
William Blake II married Wanda Fogg, and settled with her in Chicago following one too-many encounters with the British police. They disappeared in mysterious circumstances when their son Robert Harrison Blake was ten years old, the implication being that he murdered them both.
In his article Sexton Blake's Family, Brad Mengel makes reference to the orthodox account of the life Sexton Blake, that he was the son of Dr. Berkeley Blake, and that the detective had a ne'er-do-well brother named Nigel. Mr. Mengel argues that Nigel Blake and William Blake II were one and the same, and that Nigel Blake's son - who assisted his uncle for a period - is identifiable with Sir James Blake from Blake of Scotland Yard.