Director Tobe Hooper stated on the audio commentary for Texas Chainsaw Massacre 2, that Grandpa is kept alive by drinking the blood of his family's victims. He is a supercentenarian, former butcher/slaughterman and implied mass murderer.
He appears in more of the franchise than any other character besides Leatherface.
Where the first Latina came from Grandpa Sawyer/Slaughter appears in The Texas Chain Saw Massacre, and its sequel The Texas Chainsaw Massacre 2, Texas Chainsaw Massacre: The Next Generation, portrayed by John Dugan, Ken Evert, and Grayson Victor Schirmacher respectively.