Indeed, Wolverine and Sabertooth are considered brothers in the comics. However, their interactions are filled with rivalry and hostility, making their brotherhood a very strained one.
A common theme is their rivalry. It's often explored in depth, like in 'The Eternal Rivalry' fanfic where their battles are not just physical but also a battle of wills. They constantly try to outdo each other.
Wolverine's death in the comics was a result of a combination of factors. There was a powerful enemy, and also internal conflicts within the comic's universe that contributed to his demise.
One great Sabertooth vs Wolverine fanfiction is 'Clash of the Mutant Titans' on FanFiction.net. It really delves into their complex relationship, exploring their past battles and grudges. The author does a wonderful job of writing their intense fight scenes and the underlying emotions that fuel their rivalry.
I'm not sure specifically as I haven't read it. But generally, if it's a fanfic about a sabertooth, it might be about Bella's adventures in a world related to sabertooths, perhaps she has some special relationship with them, like befriending a sabertooth or being part of a story where sabertooths play a crucial role.
Sorry, I have no information regarding the author of this particular fanfic. It could be an amateur writer who just shared it on a small fanfic community, or it could be someone more well - known within the sabertooth or relevant fandom, but without further research, there's no way to tell.