Sirius Black was different from the rest of his family in the fact that he didn’t buy into the “pure blood mania” like some pure blood wizards/witches did. He ended up being disowned by his family for this and he even broke tradition by being sorted into Gryffindor when he went to school at Hogwarts instead of being sorted into Slytherin like the rest of his family.
“When this is all over, we’ll be a proper family. You’ll see.” (Order of the Phoenix)
“If you want to see what a man’s like, take a good look at how he treats his inferiors, not his equals.” (Goblet of Fire)
“We’ve all got both light and dark inside us. What matter is the part that we choose to act on. That’s who we really are.” (Order of the Phoenix)
“What’s life without a little risk?” (Order of the Phoenix)
“The ones who love us never really leave us, you can always find them here.” (Prisoner of Azkaban)