Hesper Black

Hester Black was an early member of the House of Black. She was a pure-blood witch, and it is possible that Licorus, Alexia Walkin, Phoebe and Eduardus Limette were her siblings. She never married.

Behind the scenes

Based on a statement by Horace Slughorn, this character may have been a member of Slytherin house ^[1]. However, she attended Hogwarts in the 1830s, when Slughorn wasn't even born.
This character appears only on the version of the Black family tree shown in the film adaptation of Harry Potter and the Order of the Phoenix. She was not included on the version of the tree which J. K. Rowling gave to a charity auction in 2006^[2]. However, according to director David Yates, Rowling provided the filmmakers with a copy of the Black family tree going back eight generations^[3]. The filmmakers presumably received a more complete version of the tree than the one auctioned off, which only goes back six generations.
On the Black Family tree depicted on the 2nd DVD of Harry Potter and the Order of the Phoenix, this Black's picture is depicted as a skull. Regulus is also depicted in the same way, and it is unknown why some people have skulls instead of pictures. It is possible that the skull denotes those Blacks who have died violent deaths, as opposed to natural causes.^[4]
The skull bears a striking resemblance to the Death's Heads worn by the Nazis SS troopers during the Second World War. This may simply be coincidence or it could be done to emphasize the support for repression of certain groups of people exhibited by several prominent Blacks (support of Muggle-hunting, et cetera).