So I'm not going to write a lot, but this is John Polidori. He was the personal physician to Lord Byron and also a poet and writer in his own right. He is credited with inventing the vampire story.
For more information on this please read this article (it was really good):
The Poet, the Physician and the Birth of the Modern Vampire
From that famed night of ghost-stories in a Lake Geneva villa in 1816, as well as Frankenstein’s monster, there arose that other great figure of 19th-century gothic fiction – the vampire – a creation of Lord Byron’s personal physician John Polidori. Andrew McConnell Stott explores how a fractious relationship between Polidori and his poet employer lies behind the tale, with Byron himself providing a model for the blood-sucking aristocratic figure of the legend we are familiar with today.