10. Venus and Serena Williams
All right. If youre going to let us get away with triplets, and youre going to let us get away with the Budchen twins, then maybe youll let us get away with this! While the Williams sisters are not technically twins (they were born a year apart), they might as well be. These two have played side-by-side with one another for such a long time that theyre practically Siamese twins on the court. One or another might have their favorite of the two, but theres no denying that they both kick ass.