But the Harbaughs already strain credulity - individually and as possible Super Bowl opponents.
Jim Harbaugh is bucking three trends just to be coaching San Francisco in the NFC championship game. He is a first-year head coach who was apparently not hampered in any way by the NFL lockout. He jumped to the NFL from the college level, a move that results in far more pratfalls than successes. And he was a longtime NFL quarterback, which is a better launching pad for a career in broadcasting than coaching.
John Harbaugh may have taken an even more improbable road to his second AFC title game as head coach of the Baltimore Ravens. Twenty-five years ago, he was planning to attend law school rather than follow his father, Jack, into the family business. A last-minute change of heart, and one disappointed mother, led Harbaugh on his current path - which took a long, long detour in Philadelphia.
That detour started in 1998, when Ray Rhodes hired John Harbaugh to coach the Eagles special teams. The special teams had been awful largely because the Eagles were awful. That season was a disaster, with Rhodes coaching under the near-certain knowledge that he would be fired. The dynamic led to a lot of tension, a lot of paranoia, and very little joy.
In that atmosphere, Harbaugh stood out. Maybe it was because we were about the same age, or maybe it was just that Harbaugh was and is arguably the nicest coach I've ever covered, but this beat writer jumped at the chance to do a long feature on the relatively unknown Harbaugh.
An interview with Jack provided a lot of insight into John as well as his brother, who was winding down his playing career at the time. John is 15 months older, but Jim is bigger and more athletic, and, well, there was something else. As Jack put it at the time, everyone loved John and everyone thought Jim was, you know, kind of a jerk.
Childhood friend Mike McCartney, then an Eagles personnel guy, said John was maybe the nicest guy he'd ever met. "His brother Jim? I couldn't say that about him," McCartney said.
This aura allowed John to remain with the Eagles after Andy Reid replaced Rhodes in 1999. But that also kept John pigeonholed as a special-teams coach for the next six years. It wasn't until 2007, when Steve Spagnuolo left to become defensive coordinator of the New York Giants, that Harbaugh moved to secondary coach.
A year later, he was head coach of the Ravens. At the time, he was a puzzling and unpopular choice with fans who hoped defensive coach Rex Ryan would succeed Brian Billick. But a trip to the conference championship game in his first season won the fans over.
And now younger/big brother Jim has accomplished that same feat in his first season as an NFL head coach.
No head coach has jumped directly from college football to win a Super Bowl. Just a few ex-players have won Super Bowls as head coaches: Tony Dungy, Bill Cowher, and Mike Ditka among them. Only one former NFL quarterback, the Raiders' Tom Flores, has ever won the Super Bowl as a head coach.
But here is Jim Harbaugh. His 13-3 record is two wins better than his best season as a quarterback. Harbaugh's single biggest contribution to an NFL team might have been going 2-9 as a starter for the 1997 Colts. That got the coaching staff (including defensive coordinator Jim Johnson) fired and earned Indy the No. 1 pick in the draft. The Colts used it on a guy named Peyton Manning.
Until his 49ers outgunned New Orleans last week, Harbaugh received the most attention for his obnoxiously hard slap at the hand of Detroit coach Jim Schwartz. If anything demonstrated the difference between him and his personable brother, that was it.
Now the Harbaugh brothers are in the NFL's final four. They will coach for the chance to face each other in the Super Bowl. It is a preposterous notion that the brothers, nasty and nice, have made feel inevitable.
Contact Phil Sheridan at 215-854-2844, email@example.com, or @Sheridanscribe on Twitter. Read his blog, "Philabuster," at http://go.philly.com/philabuster Read his columns at www.philly.com/philsheridan