Grandpa Sawyer/1st Timeline

Grandpa Sawyer is the grandfather and oldest living member of the Sawyer Family. He is a supercentenarian, former butcher/slaughterman and mass murderer. 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.

Biography
Grandpa was originally a worker at a slaughterhouse whose skills at killing and butchering cattle were unmatched. After modern machinery was implemented at abattoirs for butchering animals, Grandpa retired from his work, ashamed. Even decades later, the Sawyer descendants regarded slaughterhouse machinery with disdain. Grandpa apparently settled down with the unnamed Grandma and began a family, the cannibalistic Sawyers (how they became cannibalistic is never revealed, though it is implied that they resorted to cannibalism to survive starvation, because the family was already poor when Grandpa and the rest of his family quit working).

The Texas Chain Saw Massacre
Initially thought to be already dead; he is first seen briefly during Leatherface's chase scene, Sally approaches him seeking help but assumes he is dead when she sees how old he is. Later after heroine Hardesty Sally Hardesty is captured by his grandchildren, Drayton, Leatherface and The Hitchhiker, Grandpa is taken from the second floor of the house and brought to her by them. Leatherface cuts Sally's finger and forces it into Grandpa's mouth, so he can suck her blood, an event that causes Sally to fall unconscious. Sometime after Sally is awakened, Drayton, Leatherface and the Hitchhiker decide to allow Grandpa to end her life using a hammer; due to his advanced age, Grandpa is largely incapable of using the hammer efficiently and continues to drop it. The hassle that ensues with Grandpa's continued dropping of the hammer and his grandchildren's over-eagerness to help him allows Sally to break free of the Sawyer family and jump out a window, though he and Drayton do not attempt to follow her.

The Texas Chainsaw Massacre Part 2
Grandpa, now 137 years old, later appears in The Texas Chainsaw Massacre 2, inhabiting an abandoned theme park named the "Texas Battle Land" with what remains of his family; when the film's heroine, Vanita "Stretch" Brock, is captured by his grandson Chop Top, Grandpa is brought forth to kill her (in the same way he tried to do to Sally) with help from Chop Top, unlike in the first film here he actually lands a hit though he succeeds in only causing a minor head wound to her with a sledgehammer (and a second wound caused by an impatient Drayton). When Lieutenant "Lefty" Enright, the film's male protagonist, engages in a chainsaw duel with Leatherface, Grandpa attempts to aid his grandson by throwing a hammer at his opponent, only to hit Leatherface instead and subsequently fall to the floor (which alludes the first film's climax). Grandpa apparently meets his demise when a grenade, set off by an injured Drayton, explodes and kills Lefty and Drayton while injuring Leatherface.

Leatherface: The Texas Chainsaw Massacre III
Grandpa appears only as a decayed corpse kept and treated as if he were alive by Leatherface and his extended family who regularly pour blood into his mouth to "feed" him; when one of the film's protagonists, Benny, opens fire on the Sawyer house with an automatic rifle, Grandpa's body takes several shots to the chest and one to the face. In this film, the character of Mama mentions that she castrated both herself and "Papa", referring to Grandpa, implying that he raped her, and that's how her sons were convinced.

Texas Chainsaw Massacre: The Next Generation
Grandpa is mostly seen in the background, he has a very minor role in the film and is mostly present during the dinner scene.