"I really like her style, she plays not like a typical woman, she gets lots of spin and she serves really well. I'd like to serve like that," said Carolina.
David said his girls were very driven and their hard work was starting to pay off.
Both had been playing in the tough Southern competition, which pits tennis players against others from nine states.
"It's the strongest competition in the country. There's a lot of depth and a lot of top players have come from there," said David.
Jade has a ranking of 35 and Carolina is ranked 52 in the Southern 16 and under category.
Although the girls had played club tennis while living in New Zealand for six years, they did not play competitively because of the link to their famous uncle, said David.
"I was probably being a little over protective of them. Being a Lewis, I didn't want to put the pressure on them. The time is right for them now and they're certainly making up for lost time."