Pollux Black (1912 – 1990) was a pure-blood wizard, the eldest child of Cygnus Black II and Violetta Bulstrode, the brother of Cassiopeia Black, Marius Black, and Dorea Black, the husband of Irma Crabbe, the father of Walburga Black, Alphard Black, and Cygnus Black III, the grandfather of Sirius Black, Regulus Black, Bellatrix Lestrange, Andromeda Tonks, and Narcissa Malfoy, the great-grandfather of Draco Malfoy and Nymphadora Tonks, and the great-great-grandfather of Teddy Lupin and Scorpius Malfoy.
Like many members of the Black family, the name Pollux comes from a star. It is the brightest star in the constellation Gemini. The name refers to Castor and Pollux, the twin sons of Zeus and Leda in Greek mythology. The name is traditionally thought to mean "much wine", since astrologers associate Pollux with prosperity and celebration with wine. Pollux's sister Cassiopeia was named after a constellation.
Behind the scenes
- On the Black Family Tree, it states that Pollux and (possibly) Irma was thirteen years old when they had their first child. This is most likely one of the numerous mathematical mistakes made by J. K. Rowling (who frequently admits that maths is not her strong suit). Then again, it's possible Rowling is discreetly showing us that teenage pregnancy is as common in the Wizarding world as it is in the Muggle world.
- Based on a statement by Horace Slughorn, Pollux may have been a member of the Slytherin House. This is likely due to most of the Black family (with the exception of Sirius Black) being in the aforementioned House. However, he attended Hogwarts c. 1923 - 1930, when Slughorn may not have been Potions master.
- Pollux named his last son (Cygnus Black III) in honour of his father (Cygnus Black II).
- Sirius Black, a grandson of Pollux, once said that his grandfather had a Order of Merlin. That was maybe Pollux or Arcturus Black III, who was a cousin of Pollux.
- At the beginning of the tree Licorus Black is depicted with a green hat, who is very similar to Pollux, but Pollux on the image has got a red hat.
- He was thirteen years old when he had his first daughter, Walburga (although, this could just be a mathematical error on the part of J.K. Rowling). 
- Harry Potter and the Order of the Phoenix (film) (Appears on Black family tapestry)
- Harry Potter and the Deathly Hallows: Part 1 (video game) (Mentioned as Walburga Black's father)