Super Bowl XLVII would be the ultimate family gathering for the Harbaughs in New Orleans today – if only one of them did not have to lose.

John Harbaugh will coach his Baltimore Ravens against younger brother Jim and his San Francisco 49ers tonight, with parents Jack and Jackie and sister Joani trying to keep their emotions in check from the stands.

"Anybody who has a brother, especially one that's close in age, gets it," John said.

"You just grow up fighting for everything. You fight for the extra hotdog. You fight for girls. You fight for everything. We both got our girls, but we both want a victory this week."

John is only one year older but he has been Ravens coach since 2008 and has reached the play-offs five times. Jim is in his second season with the 49ers and has a 100% record of reaching the post-season himself, but defers to his brother.

"He's a great coach," Jim said. "He's very talented. I think I'm half the coach that he is but I'm trying."

The brothers grew up with football in their blood thanks to Jack, a coach all his adult life at high school and college level. None of them ever imagined endless games as children would one day lead to this. "We had our imaginary games more often in the back yard," John said.

"We were never coaches, I could tell you that. We were the quarterback and the receiver, we were the stars, we were the players.

"The truth of it is that's what this game is going to be decided by. It's not going to be about the coaches. It's about the guys playing the game and making the plays, like it always is. That's how it always plays out."

There is no question which of those players is attracting the most attention.

Baltimore Ravens middle linebacker Ray Lewis, a Super Bowl winner in 2001 and a 13-time Pro Bowler, will be playing his final professional game.

If he can end his career by defeating Jim Harbaugh, things will have come full circle for Lewis, whose first career sack was of then Indianapolis Colts quarterback - Jim Harbaugh, back in 1996.

Harbaugh insists he remembers nothing of the play, but he knows plenty about Lewis.

"Ray Lewis is one of the greatest players," he said. "He's a fine person, he's a great football player, and a man I truly respect."

The 49ers have been riding the hot arm of young quarterback Colin Kaepernick.

He was thrown in at the deep end in mid-season when Alex Smith, at the time leading the league at his position, suffered concussion in week 10, but impressed so much that Smith has not had a look-in since.