[ Her brows knit while she tries to think of how to explain. ]
If it's alright to try and explain it like this... you could think of pureblood society like a pyramid.
[She grabs her journal and draws it out as best she can.]
It looks like this.
[She goes on to try and explain.]
At the very top are the pureblood. They generally rule over the rest of the classes and are considered royalty. After them are the aristocrats, or the nobles. Their ancestry is similar to that of the pureblood, but somewhere along the way a human blood was mixed into their bloodline. The farther down the pyramid you get, the weaker the vampire.
[ She sighs heavily. ] The pureblood live for eternity. So unless... another pureblood was to match up with another pureblood, then they would be doomed to outlive their partner. It's easier for siblings in that sense. So I-- originally, I was born to be Oniisama's bride.