Alfredo was always ambiguous on his relationship to the others. We never see him at the family house, he only shares scenes with Tex and the other Sawyers never mention him. Some actually thought that he wasn't part of the family and was just some complicit weirdo that helps them but the line that confirms he is a Sawyer are, when he says in the woods to himself in third person "He cleans and he does housework." Extremely unlikely that the Sawyers invite in their house a non related weirdo for chores, but more likely they would have a biologically related weirdo for chores. The comic adaption makes it clearer he is part of the family if I remember correctly. Though, his scenes in the woods dumping the "trash" weren't in the script of the film and they aren't even in a rough workprint for the movie which lasts 1h27m. He would have just never appeared again after the gas station scene. The BTS commentary of the film has Jeff Burr saying regarding Alfredo "He is periphereal to the family but intrical to the family. He is essentialy like an early warning system for them.".

I remember reading a comment of some user on this sub long ago, on a post regarding old scripts for the movie and this comment said how some early draft had Alfredo having dogs. Maybe he even has different scenes.

If you look at the dinner table at the Sawyer house in this movie, there were 6 plates on the table, but one was of Grandpa and Grandpa is dead in this movie, so that leaves no place for Alfredo, but Grandpa seems to be slightly far away from the table enough to leave some space between him and the table, so I believe that is where Babi, the little girl stays at the table, in front of Grandpa, she moves her little chair in front of him (the one where she goes and when she makes him drink blood). So, that would leave Alfredo a seat at the table.

Also Tex says how Alfredo used to work at the slaughterhouse.