Sabretooth was one of the first mutants seen in the X-Men movies, introduced in the opening of the first 2000 film.
When Wolverine got his own spin-off story with X-Men Origins: Wolverine, though, the relationship between him and Sabretooth was finally explored; James/Logan and Victor were revealed as half-brothers and their eventual animosity was explored.
The storyline was them rising as brothers, and Liev (Schreiber) and Hugh look a lot closer in that respect, so I understand.
Sabretooth had originally been played by Tyler Mane in X-Men, but nine years later had been recast as Liev Schreiber, who played an altogether less disheveled version of Wolverine’s greatest enemy and only living family member.