What is the name of the half-human son in 'The Dunwich Horror'?

The half-human son in H. P. Lovecraft’s “The Dunwich Horror” is Wilbur Whateley. He is born in 1913 to Lavinia Whateley and the otherworldly entity Yog-Sothoth, making him only partly human.

Wilbur grows at an unnaturally rapid rate and displays extraordinary intelligence. His grandfather, Old Whateley, teaches him occult lore and helps him study the Necronomicon, which Wilbur hopes to use to summon the Old Ones. His appearance is disturbing even when he is dressed to conceal his inhuman body.

Wilbur’s most famous scene occurs at Miskatonic University, where he tries to obtain the library’s copy of the Necronomicon. After the librarian Henry Armitage refuses him access, Wilbur returns at night, but a guard dog attacks and kills him. His corpse briefly reveals his monstrous anatomy before melting away.

A common mix-up is confusing Wilbur with his invisible twin brother. The larger creature that later terrorizes Dunwich is Wilbur’s fraternal twin, who is described as resembling their nonhuman father even more closely.