Logan and Sabretooth are very similar in many ways including there intertwined past, but are the related?
Oddly enough, Sabretooth had been around for almost a decade before he actually encountered Wolverine in a Marvel comic. According to John Byrne, though, in Fantagraphics' X-MEN COMPANION II (1982), the potential for a relationship was there from the moment Sabretooth debuted in 1977's IRON FIST #14 (penciled by Byrne and written by Chris Claremont).
"In my mind, [Sabretooth] was created [with the intention of making him Wolverine's father]," Byrne recalled. "I don't think Chris originally conceived him that way, but I said, 'Hey, here's another Canadian guy who has a lot of the stuff, so I'll just draw him in such a way that he could be Wolverine's father -- or brother.' I wasn't sure in the early days." In Byrne's view, both characters were remarkably long-lived thanks to their regenerative powers. "I figure Sabretooth is 120 years old," he noted.
Officially, though, the family relationship remained purely speculative until 1991's WOLVERINE #41, wherein Sabretooth informed Wolverine that he was his father. Blood samples taken in #42 immediately disproved that notion and issue #50 took things a step further by revealing that Wolverine and Sabretooth's minds had both been implanted with myriad false memories. Among them were Sabretooth's supposed murder of Wolvie's beloved Silver Fox in the distant past (#10) and, of course, the fatherhood revelation.
The official start of their feud, according to 1992's X-MEN #6, took place more than thirty years ago in Berlin while Maverick and the two of them (then Logan and Creed) were operatives for the C.I.A. While attempting to flee Omega-Red and armed guards, Creed declared the civilian double-agent they were rescuing to be a liability -- and killed her! In the midst of their debriefing, the sickened Logan came to blows with Creed and "walked out without so much as a glance over his shoulder." As three soldiers held him back, Creed screamed, "You're MINE, boy -- and the day is gonna COME when I COLLECT!"
In the decade following his debut, Sabretooth made perhaps half a dozen appearances before Chris Claremont was reunited with his old creation (now a member of the Marauders) in the pages of 1986's UNCANNY X-MEN #212. In the process, Claremont revealed that Wolverine and Sabretooth had a shared history and Alan Davis' striking cover for #213 showed the two of 'em going at it, literally at each other's throats. It was official: Wolverine now had his opposite number.
They're fought a LOT since then, including such infamous moments as the battle in which Sabretooth pushed Wolverine too far and wound up having one of Logan's claws dislodged in his brain (1995's WOLVERINE #90). Professor Xavier actually kept the recovering Creed on the grounds of the X-Men's mansion in a continuing attempt at rehabilitating him. That ended when Sabretooth fled the grounds after nearly killing Psylocke (1995's UNCANNY X-MEN #328). And later, Sabretooth's skeleton was reinforced by adamantium as Wolverine's once was (1998's WOLVERINE #126). Unfortunately for Creed, Apocalypse decided that Logan's bones needed the adamantium more than he did and pulled it from Sabretooth's body to Wolverine's (1999's WOLVERINE #145).
The feud's still going on today. Hope they've got a lot of band-aids.