British number one Andy Murray will take on his brother Jamie for the first time at the Rogers Cup in Montreal, Canada.
The pair have never played each other before as professionals and that got us thinking about some of the other great sibling rivalries in sport.
Venus vs Serena Williams
It's one of the longest running sisterly rivalries and one of the closest.
Both Venus and Serena have been world number one and both have won multiple tennis Grand Slams.
Venus is older, by just over a year, but Serena was the first to win a major tournament, taking the US Open title in 1999 aged just 18.
HEAD TO HEAD
Venus v Serena
46 CAREER TITLES 68
7 GRAND SLAMS 21
1 BEST WORLD RANKING 1
They've played each other 26 times in their careers, including eight grand slam singles finals with Serena winning six of those.
But despite the fact they've competed against each other for so long they've also played in several doubles tournaments together, winning 13 Grand Slams and three Olympic gold medals as a pair.
Vitali and Wladimir Klitschko
When it comes to going up against your own brother there's few more brutal sports to do it in than boxing.
That might be why Ukranian heavyweights Vitali and Wladimir Klitschko have never actually gone toe to toe in the ring.
HEAD TO HEAD
VITALI v WLADIMIR
47 FIGHTS 67
45 WINS 64
2 LOSSES 3
Together they've ruled the heavyweight division for more than 15 years, both holding different world titles at different times.
Vitali won his first world belt in 1999 with Wladimir having to wait until 2006.
Wladimir is still going, making him the second longest reigning world champion in heavyweight history, but Vitali retired in 2013 having only ever lost two fights.
Becky and Ellie Downie
One of the newest sibling rivalries on the block, gymnasts Becky and Ellie Downie have competed with and against each other at the senior level for just over a year.
Becky is older and won a team silver at the European Championships when her sister was still in infants school.
HEAD TO HEAD
BECKY v ELLIE
23 AGE 16
9 MAJOR MEDALS 1
2 OLYMPICS ATTENDED 0
0 JUNIOR MEDALS 4
She also competed for team GB at the 2008 Olympics and was reserve for the 2012 London games before Ellie joined her on the team for the 2015 European Championships in France.
The sisterly combination worked a treat with both girls winning medals. Aged just 15, Ellie became the first female gymnast ever to win an individual all-around medal for Great Britain at the games, with a bronze.
Becky picked up three silvers in the uneven bars, balance beam and team event.