NEW YORK Jan 24 (Reuters) - While Baltimore Ravens head coach John Harbaugh and his brother Jim, the head coach of the San Francisco 49ers, will be the first brothers to oppose each other in the Super Bowl, plenty of other families have fought it out in the sports world:
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Venus and Serena Williams (Tennis)
Both are great players in their own right, with Serena winning 15 grand slam singles titles and Venus, the older of the two, collecting seven.
The pair squared off in eight grand slam finals, including four in a row, with Serena winning six and Venus two. In 2002 and 2003, the sisters met in four straight grand slam finals with Serena winning the lot to become just the fifth woman to hold all four titles at the same time.
When they team up in doubles, they are almost unbeatable, winning 13 grand slam titles and three Olympic golds.
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Scott and Rob Niedermayer (Ice hockey)
Scott, an All-Star defenseman with the New Jersey Devils, won a Stanley Cup and family bragging rights in 2003 when his team beat younger brother Rob and the Anaheim Mighty Ducks to hoist the treasured silver mug.
The Niedermayer boys became the first brothers to meet in a Stanley Cup finals since the Boston Bruins' Terry Reardon and Montreal Canadiens' Kenny Reardon clashed in 1946.
Later in their careers, they joined forces in Anaheim and won the 2007 Stanley Cup together with the Ducks.
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Alistair and Jonathan Brownlee (Triathlon)
Until last month the British brothers shared a house in northern England and did all their training alongside each other but come race time it was always every man for himself.
After frequenting the podium together in many top level races, the duo delivered again when it really mattered when Alistair Brownlee, older by two years, won the triathlon gold medal at the 2012 Olympics, with Jonny taking bronze.
Alistair had been world champion in 2009 and 2011 (with Jonny finishing second) but his injury-absence from early races this season allowed Jonny to step up and take the 2012 title.
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Jerome and Kevin-Prince Boateng (Soccer)
Half brothers Jerome and Kevin-Prince Boateng became the first siblings to play against each other at the World Cup when they found themselves on opposing teams in South Africa in 2010.
Jerome played for Germany, where the pair were raised, while Kevin-Prince, one year older than his sibling, represented Ghana. Germany won the group match 1-0 but both teams advanced to the next round.
The pair were not on the best terms in the lead up to the match because of an incident that happened the previous month when Kevin-Prince made a clumsy tackle on German captain Michael Ballack in the English FA Cup final. Ballack suffered a broken leg and missed the World Cup.
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Michael and Ralf Schumacher (Motor racing)
The Schumachers raced against each other in Formula One between 1997 and 2006, with Ralf growing up in the shadow of older sibling Michael and never escaping it.
Ralf's six wins made him Germany's second most successful F1 driver of all time until the arrival of Sebastian Vettel but that was nothing compared to Michael's 91 victories.
The Schumacher name undoubtedly helped Ralf into Formula One but it also proved a curse by comparison.
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Ken and Clete Boyer (Baseball)
Ken and Clete were the opposing third basemen in the 1964 World Series between the New York Yankees and St. Louis Cardinals.
The Fall Classic went all the way to a seventh game and both brothers played starring roles, each hitting home runs in the decider. Clete, six years younger, had already won the World Series twice before with the Yankees but in 1964, it was Ken's Cardinals that triumphed.
Two other sets of brothers also met in the World Series. In 1920, Jimmy (Brooklyn Robins) and Doc Johnston (Cleveland Indians) faced each other, with the Indians winning. In 1921, 1922 and 1923, Bob Meusel (New York Yankees) and Irish (New York Giants), squared off. Irish, the older of the pair, was on the winning team in 1921 and 1922 but Bob, playing alongside Babe Ruth, got the last laugh by triumphing in 1923.
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Phil and Steve Mahre (Alpine skiing)
Phil Mahre was born four minutes earlier than his twin brother Steve but the pair were even closer on the piste.
At the 1984 Sarajevo Winter Olympics, the siblings battled it out for the gold medal in the men's slalom.
Steve led after the first of two runs, with Phil third, but their positions were reversed after the final run with Phil winning the gold medal and Steve the silver, by just 0.21 seconds. - - -
Aldo and Nedo Nadi (Fencing)
The Italian brothers were the greatest fencers of their generation.
At the 1920 Olympics in Antwerp, Aldo, the younger of the pair, won three gold medals, only to be outdone by Nedo, who five, the record tally at a single Olympics until American swimmer Mark Spitz won seven golds in 1972.
The pair were on the same side in the foil, epee and sabre team events but Nedo also won the individual foil and sabre events. Nedo finished second to his brother in the sabre.
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Adi and Rudi Dassler (Sports business)
Sibling rivalry in sport is not restricted to the field of play as the German Dassler brothers demonstrated in their family feud in the sports shoe business.
Adi founded the company that later became known as Adidas and Rudi joined him in the business, which began to expand internationally after American Jesse Owens wore their shoes at the 1936 Berlin Olympics.
But the brothers fell out during World War Two in 1948, Rudi parted ways and established his own company, Puma, in the same German town where Adidas was based, setting the tone for a rift that continued until both men died in the 1970s.
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Wladimir and Vitali Klitschko (Boxing)
Sibling rivalry can prove too much of a strain for some families - to such an extent that siblings rule out competition altogether.
Between them, Wladimir and Vitali dominate world boxing's heavyweight division, but there is no chance of the belts being unified as the Ukrainian pair refuse to fight each other. (Compiled by Julian Linden; editing by Gene Cherry)