From tennis courts to baseball diamonds, the sporting world has seen much sibling rivalry, but the National Football League's quarterbacking brothers Eli and Peyton Manning may be the first to come with Roman numerals.

Manning Bowl II grabs the NFL spotlight on Sunday when Eli leads the New York Giants into Indianapolis to take on older brother Peyton and the Colts in a prime-time family feud.

There have been over 333 documented sets of brothers who have played professional football, but perhaps no one can relate to that dilemma more than two sisters.

Tennis siblings Venus and Serena Williams, minority owners in the Miami Dolphins, know plenty about what it feels like to stare across at a family member and plan their demise having played each other 23 times, including four Wimbledon finals.