Sleep and His Half-Brother Death is a painting by John William Waterhouse completed in 1874. Waterhouse’s first Royal Academy exhibit (submitted from his father’s house at 1 Scarsdale Villas), it was painted after both his younger brothers died of tuberculosis.
https://en.wikipedia.org/wiki/Sleep_and_His_Half-Brother_Death
It’ s a reference to gods Hypnos (sleep) and Thanatos (death), who are brothers.