Oudin Twins Have No Plans to Replace Venus and Serena

So, if you think of me, like think total opposite and that's her," said Melanie, adding, "she's a nice girl too and stuff."

As different as they may be in personality and appearance, they are still two teenage sisters who enjoy talking about boys, shopping and playing tennis. For nine years, Katherine trained with Brian de Villiers, Melanie's coach, but does not share her sister's singular ambition.

"That has never been my dream," she said. "If I was a struggling pro tennis player, that would be bad. People always assume there is a jealousy thing. But that's not true at all."

"I like tennis but I don't want it to be my life," she said. "Only a few people can do that and Melanie is one."

Katherine plays first singles on her high school tennis team, the Georgia state champion in 2007 and 2008.

"Katherine is a great athlete and she is a great little tennis player too," said her mother. "But her focus has been academics."

She hopes to attend the University of Kentucky, William & Mary or Davidson College next year.