This Super Bowl will be filled with firsts — and one significant last.

The Harbaughs, San Francisco’s Jim and Baltimore’s John, will be the first pair of brothers to coach against each other in the NFL title game.

Quarterbacks Colin Kaepernick of the 49ers and Joe Flacco of the Ravens each will be playing in his first Super Bowl — where success is the ultimate measure of elite QBs.

It’ll be Baltimore’s first crack at a championship in a dozen years, San Francisco’s first in 18. They are a combined 6-0 in Super Bowls (the 49ers own five of those victories), so one club will lose the big game for the first time.

And middle linebacker Ray Lewis, Baltimore’s emotional leader and top tackler, will be playing in the final game of his 17-year career before heading into retirement.

“This is our time,” Lewis pronounced.

For all of those story lines, none is expected to command as much attention as Harbaugh vs. Harbaugh. The game in New Orleans on Feb. 3 was quickly given all manner of nicknames: The Brother Bowl. The Harbaugh Bowl. The Har-Bowl. The Super-Baugh.

The Harbaughs’ sister, Joani Crean, wrote in a text to The Associated Press: “Overwhelmed with pride for John, Jim and their families! They deserve all that has come their way! Team Harbaugh!”

As John prepared to coach the Ravens in the AFC championship game Sunday night, he watched on the stadium’s big video screen as Jim’s 49ers wrapped up the NFC championship.

John looked into a nearby TV camera, smiled broadly and said: “Hey, Jim, congratulations. You did it. You’re a great coach. Love you.”

Less than four hours later, the Ravens won, too. Some siblings try to beat each other in backyard games. These guys will do it in the biggest game of all.

Who’s a parent to cheer for?

During the 2011 regular season, the Harbaughs became the only brothers to coach against each other in any NFL game (the Ravens beat the 49ers 16-6 on Thanksgiving Day that year).

The NFC West champion 49ers (13-4-1) opened as 5-point favorites, seeking a record-tying sixth Super Bowl title to add to those won by Hall of Fame quarterbacks Joe Montana and Steve Young.

Lewis was the MVP when the AFC North champion Ravens (13-6) beat the New York Giants in 2001.

With Kaepernick’s terrific passing — he was 16 of 21 for 233 yards and a touchdown in only his ninth career NFL start — and two TD runs by Frank Gore, San Francisco erased a 17-point deficit to beat the Atlanta Falcons 28-24 Sunday.

Baltimore then fashioned a comeback of its own, scoring the last 21 points to defeat the New England Patriots 28-13, thanks in large part to Flacco’s three second-half touchdown tosses, two to Anquan Boldin. Lewis and the rest of Baltimore’s defense limited the high-scoring Patriots to one touchdown.

In the often risk-averse NFL, each Harbaugh made a critical change late in the regular season in a bid to boost his team’s postseason chances. Clearly, both moves worked.

After 49ers quarterback Alex Smith, the starter in last season’s overtime NFC title game loss to the Giants, got a concussion, Jim switched to Kaepernick for Week 11 — and never switched back. Now San Francisco has its first three-game winning streak of the season, at precisely the right time.

Baltimore, meanwhile, was in the midst of a three-game losing streak when John fired offensive coordinator Cam Cameron and promoted quarterbacks coach Jim Caldwell to replace him.

The 50-year-old John is 15 months older than Jim and generally the less demonstrative of the pair, although John certainly did not lack intensity while making his case with officials a couple of times Sunday.

The ever-excitable Jim — who was treated for an irregular heartbeat in November — was up to his usual sideline antics in Atlanta.

He spun around and sent his headset flying when the original call stood after he threw his red challenge flag on a catch by the Falcons. He hopped and yelled at his defense to get off the field after their key fourth-down stop with less than 1½ minutes left. He made an emphatic-as-can-be timeout signal with 13 seconds remaining.

Expect CBS to fill plenty of time during its Super Bowl broadcast with shots of Jim, that trademark red pen dangling in front of his chest, and John, who usually wears a black Ravens hat. That is sure to be a focal point, right up until they meet for a postgame handshake in two weeks’ time.

AP Sports Writer Janie McCauley in San Francisco contributed to this report.