Sirius bucked the trend in the Black family by being sorted into Gryffindor as opposed to Slytherin, like the rest of his family. This marked him as being different from the off and him being a Gryffindor – coupled with a significantly more sympathetic disposition – resulted in a rocky relationship with his family.
At Hogwarts, she, along with her sisters, was sorted into Slytherin. It is suggested in the novels that, as a student, Bellatrix associated with a group of students – including Rodolphus Lestrange, Severus Snape, Avery, Evan Rosier and Wilkes – who nearly all became Death Eaters.
Sorted into Gryffindor house, Remus Lupin was swiftly befriended by two cheerful, confident and rebellious boys, James Potter and Sirius Black. They were attracted by Remus's quiet sense of humour and a kindness that they valued, even if they did not always possess it themselves.
He rejected his family's pure-blood elitism and reverence for the Dark Arts. At Hogwarts, rather than be sorted into Slytherin like the rest of his family, Sirius was placed in Gryffindor. In contrast to his home life, Sirius greatly enjoyed life at Hogwarts, where he was inseparable from his best friend, James Potter.
In Half-Blood Prince, Ch. 4, Horace Slughorn states: "The whole Black family had been in my house, but Sirius ended up in Gryffindor!... I got his brother Regulus when he came along, but I'd have liked the set." This implies that all Blacks except Sirius were Sorted into Slytherin while Slughorn was Head of House.
Bellatrix Lestrange, Narcissa Malfoy, and Sirius Black are all descendants of Pollux Black, making them first cousins. Note: For space's sake, this tree doesn't include Andromeda Tonks or her husband and daughter. Sirius had good reason to avoid his relatives, as many in his family served as Death Eaters.
Mad-Eye Moody Is a Hufflepuff.
The Malfoys are related to the Black family through Narcissa (a first cousin of Sirius Black, Harry's godfather), which makes Draco a nephew of both Bellatrix Lestrange and Andromeda Tonks. Draco is also Nymphadora Tonks' first cousin through their mothers.
At the end of GOF only a handful of people even know that Sirius is an animagus, let alone his loveable big doggie form. But by the beginning of OOTP we have Lucius Malfoy able to "recognize" Sirius by seeing the large black dog with Harry. So we're left with a good mystery.
But what makes him a Gryffindor? Funnily enough, Harry Potter himself provides us with an answer. It's possible to influence the Sorting Hat with your own wishes and desires. This is the key reason Peter Pettigrew became a Gryffindor.
When James learned what Sirius did, he stopped Snape before he reached the Shrieking Shack, saving his life. Snape, however, had seen Lupin in werewolf form and was sworn to secrecy by Dumbledore.
Albus Potter goes to Hogwarts. He is Sorted into Slytherin House.
Any Hogwarts house would have been lucky to count Nymphadora Tonks amongst its numbers, but with apologies to Gryffindor, Slytherin and Ravenclaw – this witch is Hufflepuff through and through.
In Deathly Hallows - Part 2, Harry, Ron and Hermione deduce that the cup is being stored in the Gringotts vault of the Lestranges, a family deeply dedicated to Voldemort. After breaking into the vault and stealing the cup, Hermione destroys this Horcrux in the Chamber of Secrets with a Basilisk fang.
Draco Malfoy's mother Narcissa was cold, cunning and devoted to the Dark Lord. But she was also a mother, which meant she was willing to risk everything to make sure her son was safe. When Harry survived Voldemort's Killing Curse for the second time, Narcissa pretended he was dead so she could get to Draco.
In some cases (the Malfoy family) blood traitors are a bad as Mudbloods. As other people said, it is also due to the Malfoys' arrogance, the feeling of self-importance and wealth. The Weasly family is also very poor, which may also lead to a dislike with the rich, pureblood families.
She asked him because if Draco was still alive, she had something to fight for. She had a reason to lie to Voldemort. If Draco is alive, she needs to get into the school to see him and protect him, and helping Harry feign death was the easiest way to do that. But if Draco was already dead, she wouldn't have bothered.
Even J.K. Rowling says that Hufflepuff is her favorite House. It's produced the fewest Dark wizards of all four Houses. Hufflepuffs are down-to-earth. Literally, their House colors represent wheat and dirt, symbolizing their humility (rather than the precious metal secondary colors of the other Houses).
It is revealed that The Order of the Phoenix was betrayed by Kreacher, Sirius Black's house elf, when Sirius, in a fit of anger, gave Kreacher an order that permitted him to speak to Sirius' cousin, Narcissa Malfoy.
Book 1 - The Prince of Slytherin
Grindelwald is mentioned by Ron Weasley, who erroneously states he was sorted into Slytherin House at Hogwarts.