Thanksgiving night isn't the first time that John and Jim Harbaugh have squared off.
In the Harbaugh household, there was a tape line in the middle of the brothers' room, and as John puts it, you didn't cross it unless you were prepared to fight. There was that challenging slope in the backyard that caused arguments on whose turn it was to mow it. And there was that family vacation that resulted in a wrestling match on the beach ... when the brothers were in their mid-20s.
John and Jim Harbaugh acted like most brothers growing up, but they're not just any pair of siblings Thursday night. On a day when football and family goes hand in hand, they become the first brothers to go against each other as NFL head coaches when the San Francisco 49ers, coached by Jim, play at the Baltimore Ravens, coached by John. Both have led their teams atop their divisions and are seeking first-round byes in the playoffs.
It's historic, pressure-filled and somewhat complicated. The Harbaughs are their own biggest supporters, defenders and confidants. They've always been teammates, on and off the field. They consider themselves best friends. In fact, they've faced each other in an official game only once before. It was high school American Legion baseball, and John's team won, 1-0.
For the Brothers Harbaugh, it's more about sibling respect than rivalry.
"I have never rooted against him, really, ever," John Harbaugh said.
This is just as tough on the family. It's one of the reasons why Jim Harbaugh chose a head-coaching job in the NFC, so this would happen once every four years.
John and Jim's parents, Jack and Jackie, usually watch John's early afternoon game followed by Jim's later afternoon one. They will be in Baltimore for this game, but only briefly. The parents will pose for a pregame picture on the field and go to a place where they can watch the game privately on television.
"We know it’s going to be emotional, we’re just not sure what emotions we’re going to experience," Jack said. "It’s such uncharted waters."
Jack and Jackie's 50th wedding anniversary is the day after the game. That will be time for celebration. Thursday night could be a time of consternation.
The parents can't root for one son because it means rooting against the other. Neither will wear purple or scarlet red and gold that day.
"If it ends in a tie," Jackie said, "wouldn't that be wonderful?"
That would be fitting considering the closeness of the brothers. John was born in 1962. Jim was born in 1963. They shared a room together for 16 years and much, much more.
When John Harbaugh became coach of the Ravens, he wanted a blue-collar mentality so he handed out blue-collar shirts to his players. Jim did the same thing this year with the 49ers.
When Jim Harbaugh was coach at Stanford, he had a sign that read: "Stanford football is hustle. Constant hustle. Hustling all the time." John has that same sign -- with Stanford being replaced by Ravens -- hanging outside an office.
"Sharing ideas, sharing goals, sharing dreams. We've been doing it our whole lives," Jim Harbaugh said.
Both are highly emotional coaches. Jim Harbaugh got into an on-field confrontation with Detroit coach Jim Schwartz earlier this year after an overly aggressive handshake. A few weeks later, John Harbaugh came into the postgame news conference in Pittsburgh with a bloodied gash on his chin because he hurt himself while making a celebratory leap at general manager Ozzie Newsome.
Their parents know how physical John and Jim can get and often had to become referees between the two.
"We had some knockdown drag-outs when we were younger," John Harbaugh said. "I can remember my mom screaming, whaling and crying, ‘You're brothers! You are not supposed to act like this! You're supposed to get along better!' There are probably a lot of mothers out there that can relate to that."
The brothers, though, have fought for each other as adults (albeit that one time when Jim got John in a headlock at the beach). John could have been jealous of Jim playing quarterback at Michigan and the NFL. Jim could have been envious of John becoming an NFL head coach first.
John still calls Jim the most underrated quarterback that ever played. "If you can’t root for your brother," John said, "I don’t know who you could possibly root for in the world."
Jim believes John's success as an NFL head coach paved the way for him by putting out the notion, "Maybe Jim's just cut from the same cloth."
Some suggest the brothers are different in their approaches. John is often characterized as the cerebral one, and Jim gets the competitive label.
“Put a brick wall in front of Jim, and he’ll run through it," said Matt Weiss, who has been John's assistant for the past three years and worked under Jim from 2005 to 2008. "Put that wall in front of John, and he’ll find three ways around it.”
Before this season, John and Jim would take once a week or once a month to talk football. They would exchange thoughts, strategies and approaches.
"He's a guy I trust the most and would entrust him with absolutely anything in my life," John Harbaugh said.
The relationship has changed since the 2011 schedule was announced.
“Leading up to this, John has talked freely and openly about football with me," Jim Harbaugh said. "Now, it’s more talking in code. I’m being serious. I can see there are limitations to what he’s telling me. I thought love had no boundaries, but now I see that it does.”
But they still act like brothers these days. Just look at the back-and-forth between them surrounding buying tickets for all of the family members attending the game.
"That's been kind of an expensive proposition," John Harbaugh said. "I haven't heard from Jim. I haven't really gotten an offer. I was surprised about that."
When reporters asked Jim Harbaugh for a response to that, he said: "I'm not really adding up who's doing more or paying more. We're not keeping score. We'll keep score in the game."
John and Jim have got their teams on similar paths. John Harbaugh is on pace to guide the Ravens into the playoffs for a fourth straight season. Jim Harbaugh has turned around the 49ers and has them on verge of being the first team to clinch a division title this year.
The next question that begs asking is: What would happen if the brothers met in the Super Bowl this season?
"I haven't thought about that much," Jack Harbaugh said. "As much as I can’t fathom what this is going to be like, I can’t fathom what that would be like."