Iola Black was a witch who was burned off of the Black Family Tree when she married Muggle Bob Hitchens.
Iola was the youngest of four siblings who were born in 1845, 1847, and 1850. Although she may have been born at any time after 1850, for the purposes of our timeline we assume that the pattern followed and she was born around 1853.
Iola Black was disowned by her family when she 'married Muggle Bob Hitchens', as represented by a burn hole in the Black Family Tree (key#1). Her parentage not given. She was the youngest of four siblings, the older being Sirius, Phineas Nigellus, and Elladora (BFT).
Iola = Gr. violet-colored dawn
Iola = Welsh valued by the Lord (source)
Original reports of the names from the Black Family Tree were gained by fans who memorized what they saw when they visited the original document on display before the auction. As might be expected, a few details that these fans memorized as best they could were later proven incorrect, including the name of Iola Black. Some sources still list her name as Isla, which was the name that had been reported by fans who viewed the original. A full image of Rowling's hand-drawn original has since been made available and the name proved to be Iola instead of Isla.