The Black family from Harry Potter were an interesting bunch. Although not main characters of the series, for the most part, a lot of information about them leaked out through the other characters and through J.K. Rowling herself. They were definitely an odd bunch — proud pure-bloods, with some eccentricities that are pretty hard to ignore. It doesn't seem harsh at all to claim that they were, hands down, one of the most messed up families in the series — awful, supremacist, and often unhinged.
A few facts aren't mentioned in the books, or didn't have a heavy emphasis, but they'll make you pause and think because, wow... just how strange does this family get?
Mottos aren't a big thing for families in the Potterverse. They're more of a Game of Thrones style of thing — but the Black family loved having a motto and displayed it proudly on their tree.
It means 'always pure', and was a reference to the pure blood they were so proud of. The Black family had a habit of blasting anyone off their family tree who might taint their reputation, and were very proud of their supremacist stance against non-magical blood. An odd thing to be proud of, but this family weren't exactly sane. We're just beginning to scratch the surface here.
Sirius and Regulus were brought up in the exact same environment, with the same parents, and yet turned out to be completely different. A good old 'nature is more important than nurture' argument.
Or is it?
Initially, Sirius was the rebel; the one who didn't believe in his parents teachings, shockingly unprejudiced for someone who grew up as privileged as he did. Regulus was the favorite of Walburga and Orion, presumably pinning all their hopes on him because Sirius had turned out to be such a disappointment. They were opposite brothers.
For a while, anyway.
Regulus bravely defected from the Death Eaters eventually and made a pretty decent attempt at getting rid of Voldemort, so maybe he took after his big brother more than anyone thought.
It's weird to think of the Black family being so closely related to the Weasleys, but all pure-blood families are related. Much as the Black family probably don't like to admit it, since the Weasleys are what's considered 'blood traitors' — those pure-bloods who take no pride in their heritage, and aren't prejudiced against those of 'lesser' blood.
Cedrella Black married Septimus Weasley and was subsequently disowned for following her heart. She wasn't the last member of the family this happened to, but apparently the Black family had really strict conditions for which families they could marry into. After all, at least Septimus was a pure-blood.
Cygnus III and his father, Pollux, back in the day both had kids at thirteen.
While not impossible, and it doesn't inherently mean anything bad, it's pretty strange that both men had children as young as thirteen since that's an incredibly young age to be procreating. Fans have put this down to J.K. Rowling's self-confessed bad math, as surely she didn't intend for two generations of the family to be having children when they were barely adults themselves, but she might well have. Two generations in a row? Like father, like son.
Like a lot of pure-blood families, the Black family tends to own House-Elves. House-Elves are creatures who are treated as slaves, and tend to become very attached to the family they're serving. The Black family went one step above in their cruelty and would behead the House-Elves who got too old to serve them.
The House-Elves, of course, considered it an honor. The Stockholm Syndrome was very real in this relationship.
They kept the heads — a barbaric tradition — although Kreacher fortunately escaped this fate since all the Black family died before he did. Still, the poor House-Elves who came before him and were not quite so lucky.
It's not unusual in the Potterverse for portraits to exist of dead characters, letting their spirits live on through that. Dumbledore's portrait was even able to offer advice.
Walburga's portrait, however...
Sirius' mother kept a portrait of herself stuck up in the Black family house that no one could remove, and she would holler and scream at anyone who passed. This had to be the most annoying portrait in the whole of the Harry Potter world, as everyone had to tiptoe quietly past her to avoid being screamed at and called a whole host of slurs for being in her home. She would have given Bellatrix a run for her money.
A slightly less serious one, but... Bellatrix, Andromeda, and Narcissa all had different hair colors.
They just didn't look alike in any fashion (well — Andromeda and Bellatrix perhaps a bit similar, but even then)...
Bellatrix had extremely dark hair. Andromeda's was light brown. Narcissa's was bright blonde — at least in the books. In the movies, it was two-toned.
In terms of the story, this was probably for aesthetic reasons in terms of each character, but in terms of biology it's pretty surprising that not even two of them had the same hair color.
Sirius was disowned for running away from home at the age of sixteen, but he was not the only one.
The Black family loved to disown people and in the same generation, Andromeda — mother of Nymphadora Tonks — was disowned for marrying a Muggle-born. It's not known if she was super sympathetic to the cause of the Order, or only helped out because of Ted and was just in love, but she clearly didn't follow her family's teachings that strongly. Impressive, considering she probably had to wriggle out from under the ever-watchful eye of Bellatrix. It's surprising that Andromeda lived until the end of the series, all things considered.