Cepheus Black II (14 September, 1657 - 11 April, 1719) was the father of Viola Black, who was known for marrying William Stuart, "the Mudblood King." He was a member of the Noble and Most Ancient House of Black, and he was a Slytherin at Hogwarts. His father-in-law, Saturnius Malfoy, was involved heavily in the plot to instill his descendants onto the British throne by inviting Prince William, the eleven-year-old son of Queen Anne and her husband, Prince George of Denmark, to Hogwarts.
Biography
Early years (1650s)
Cepheus Black II was born at one of the various Black family estates in Somerset, England. His father was Aquilinus Black, the family Lord of the House of Black, and served on the wizenagmot. Cepheus was the Heir to the Noble and Ancient House of Black until his father's death in 1700.
His mother was a muggle-born witch, which was somewhat common among pure-bloods of the time, in a world before the International Statute of Secrecy, which made wizarding marriage between muggles illegal (this was later revoked in the late 18th century), and the intermingling of their high societies illegal as well. His mother, however, was Viola of France, the daughter of King Louis XIII, who had been removed from her home country after Beauxbatons Academy of Magic refused to admit her. Although muggle-borns need to be educated, lest they become obscurials, France was struggling with controlling its muggle population and witch hunts were occurring all over the globe.
Cepheus's grandfather, Cepheus I, for whom he was named after, initiated a marriage contract between Viola and the House of Rosier and his son, Aquilinus, who married her as he was told.
Cepheus had two younger siblings, a younger brother, Regulus Black I, and a younger sister, Cyneburga.
He attended Hogwarts School of Witchcraft and Wizardry between September of 1669 and June 1676. He was a member of Slytherin House.
Introduction to Gloucester (1700)
Cepheus was instructed by Saturnius to adopt the young Prince as his son, but Saturnius' descendants would never rule over Britain: the muggle Parliament passed an Act of Settlement in 1707 that allowed the descendants of a distant cousin of Prince William's, Sophia of Hanover, to inherit the throne. Meanwhile, their adopted son William had fallen in love with their biological daughter, Viola, and Lavinia and Cepheus together never managed to produce a son that survived infancy. (One surviving son in particular, Quintus, was found to be a squib and later taken care of by Saturnius himself.) This plot was never widely known by wizardkind and as a result only a rumour, although it is perhaps the Black Family's best-kept secret. A Black never married a Malfoy again until the union of Narcissa Black and Lucius Malfoy in the 1970s, and they were ninth cousins.
In most anthologies and geneaologies, Cepheus and his wife Lavinia Malfoy are incorrectly recorded as the father and mother of the four children belonging to their daughter, Viola, and William: this may be an attempt to cover up the union of William and Viola, as their story has mostly been lost to modern ears. For example, if Orion or Walburga Black were to know that their forefathers descended directly from muggles, originally, they would have been horrified.
The Blacks and the Malfoys grew to be some of Britain's most formidable familes and champions of pureblooded law and order. However, in the days of Cepheus, his wife, Lavinia, and his father-in-law, Saturnius, purebloods marrying muggle nobility, especially those who were rich or powerful, was more acceptable.
Post-mortem
Cepheus's daughter, Viola, married Prince William, known to halfblooded and some pureblooded wizards as William Stuart, "the Mudblood King." However, some approved of the match. Muggle-born nobility around the wizarding world became to be viewed as having mostly equal status with purebloods. William and Viola's marriage, although controversial, produced four children.
Perhaps even more controversial was for the Black Family to name their descendants with the surname of their mother, as Stuart was abolished.