German brothers Alexander and Mischa Zverev have both enjoyed success in the sport, with the younger sibling enjoying a breakout year in 2016. Alexander won his first title in St. Petersburg, and became the youngest player to enter the Top 20 since Novak Djokovic. Mischa reached his highest career ranking in 2009 (No. 45), but has enjoyed a bit of a resurgence this year. He picked up his first ATP Challenger title in over eight years, as well as reached the Shanghai quarterfinals and Basel semifinals, raising his ranking to No. 51. Sibling rivalry, perhaps?
4
Venus and Serena Williams