Arcturus Black II

Arcturus Black (1884 - 1959) was the youngest son of Phineas Nigellus Black and Ursula Flint. He married Lysandra Yaxley, and the couple had three children, Callidora, Cedrella, and Charis Black. Through his daughter Cedrella, who was disowned for marrying "blood traitor" Septimus Weasley, Arcturus is the maternal grandfather of Arthur Weasley.

Etymology
Arcturus is the name of the brightest star in the constellation Boötes. Its name derives from Ancient Greek Αρκτοῦρος, meaning "bear guard"; this refers to the story in Greek mythology that Zeus placed Arcturus in the sky to look after Arcas and Callisto, who were turned into bears and then into the constellations Ursa Major and Ursa Minor to protect them from Hera's wrath.

Behind the scenes

 * Based on a statement by Horace Slughorn, Arcturus may have been a member of the Slytherin House. However, he attended Hogwarts c. 1895 - 1902, when Slughorn wasn't Potions teacher.
 * Arcturus was named after his great-uncle. After that, his nephew was named Arcturus.

Notes and references
Arcturus Black II