The son of Thomas Logan. Because of the abuse he endures at the hand of his father, he, too, becomes an abusive, hate-filled person.
Originally, he was somewhat a friend to James Howlett when he was young and frail. However, as he ages, he becomes more and more aggressive. He tries to rape Rose, a girl who cares for James, and then kills James's pet dog. Because of these two incidents, James' father, John, fires Dog's father, Thomas Logan.
In a drunken fit, Thomas Logan breaks into the Howlett's property with his son. Thomas kills John Howlett, and in turn, James kills Logan. Rose, not knowing what to do, takes James away, leaving Dog alone. When the police arrive, Dog blames the whole thing on Rose and James.
Dog is adopted by Howlett, Senior. Later, on his deathbed, Howlett wishes to make amends with his grandson, James. He sends Dog to find him. Dog tracks him so well even after so many years that it seems his tracking skills are not altogether human. Dog tries to kill Rose and James, but James trying to kill Dog ends up killing Rose. Dog has not been seen since.
Dog and Sabretooth Connection
Based on the most current data, there is no source material that states as canon in the Marvel Universe that Dog is Sabretooth. Despite this, fans on the internet have been inferring or implying the opposite.
An interviewer asked Paul Jenkins if the character Dog Logan was Sabretooth. Paul Jenkins said he had not intended it to be him, but said he wouldn't have a problem with another writer doing it later. Despite that no writer has yet written a story that Dog is Sabretooth, fans have been spreading unfounded rumors on the internet about Dog and Sabretooth. Sabretooth and Dog have similar characteristics and traits, both are big caucasian males with similar appearances, both enjoy killing, both have grudges against Wolverine, both have abusive fathers, and both possess excellent tracking skills. With no proof, fans are only able to imply or infer their ideas from these supposed similarities.
Recently, the comic X-Men Origins: Sabretooth was released, showing Sabretooth's own origin. It seems that he and Dog are really two separate characters and any similarities are just coincidental.