J.K. Rowling reveals there was another Harry Potter

J.K. Rowling has revealed Harry Potter shared his name with his great-grandfather. Photo / supplied

It is almost 20 years since JK Rowling first bewitched the world with Harry Potter, yet the author continues to excite fans by revealing small details from the magical universe.

The latest nugget of backstory concerns Harry's ancestors, and it transpires that he is not the first Harry Potter.

Henry Potter (Harry to his friends) served on the Wizengamot, the high Wizard court of law, from 1913 - 1921 and is the great-grandfather of his famous descendant, Rowling writes on the Pottermore website.

And like his great-grandson, he was not afraid to stand up for the rights of Muggles.

"Henry caused a minor stir when he publicly condemned then Minister for Magic, Archer Evermonde, who had forbidden the magical community to help Muggles waging the First World War," Rowling writes.

"His outspokenness on the behalf of the Muggle community was also a strong contributing factor in the family's exclusion from the 'Sacred Twenty-Eight'."

J.K. Rowling revealed the new information on the Pottermore website. Photo / AP

The "Sacred Twenty-Eight" is the "supposedly definitive list of pure-bloods" and its anonymous compiler suspected the Potter family "had sprung from what he considered to be tainted blood".

Henry Potter went on to have a son, called Fleamont. He and his wife Euphemia then had a son called James and they lived long enough to see him marry Lily Evans.

Sadly they died from dragon pox before they were able to meet their grandson, Harry.
The titbit thrilled fans and immediately spurred speculation of a future spin off.

Remember when @jk_rowling said she'd stop writing books?
You ready for Henry Potter aka "Harry Potter" ? #Ihearditthroughthegrapevine pic.twitter.com/IRikL2xWr7

— GewoonRúna (@gewoonRuna) June 22, 2017

Monday marks 20 years since the release of Harry Potter and the Philosopher's Stone, the first of seven Potter books in a series that sold 450 million copies in 79 languages and sparked a £5.5 billion movie franchise.