Phineas Arcturus Black (1880-1956) was a famous Muggle rights activist in the early 20th century. Phineas was also the second of Hogwarts Headmaster Phineas Nigellus Black's four sons.
Phineas was a handsome man with dark eyes that always seemed deep in thought.
Phineas had a strong opinion and usually fought with his siblings. He did try to reconcile with his father to get his son into Hogwarts.
Phineas was born as the second of five children in Hogsmeade. His parents were Headmaster and School Matron of Hogwarts.
As he supported Muggle rights and Muggle-born rights, he was cut off from the family. He eventually became an activist and married a muggle called Daphne.
He got a daughter and a son. His son was a wizard but couldn't get into Hogwarts because (in 1917) Phineas's father was stil Headmaster and forbid his grandchild from ever coming, fearing people would find out about the disinheritance.
He died in 1956 at age 76.