Let’s see: Two sisters from California, as close as can be, rise up through the tennis ranks and seem poised to become Grand Slam champions.

Sounds a little familiar, give me a second, names are on the tip of my tongue…

OK, OK, it’s far, far too soon to expect twins Annika and Kristina Penickova to become the next Serena and Venus Williams.

They’re only 14 years old, about to turn 15 (on September 11), but their progress, results and the hype around them is growing as they play the US Open Junior Championships.

But there are major differences between Annika and Kristina, and the Williams sisters, icons in the sport.

For one, Annika and Kristina are twins. We’d tell you which one is older, but no one but their parents, Tomas and Olga, know.

“They refuse to tell us!,” Kristina said. “It drives me crazy.”

“We went looking for our birth certificate once, and couldn’t find it, and then we just kind of gave up,” laughed Annika. “It really doesn’t matter.”

Another big difference is that the Penickovas are fully a part of the USTA system, whereas the Williamses were not.

Kristina and Annika now live and train at the USTA headquarters in Orlando, where they have a bevy of on-court performance coaches, as well as sessions with Dr Larry Lauer, the USTA director of mental performance.

“We’re preparing them for professional life, and everything it’s going to take to live that life as a pro player,” Lauer said. “It’s teaching them mental skills to help them be confident, and be resilient, to help them be able to perform at a consistent basis.

“You want them to experience the stress, the distractions, the adversity they’re going to face when they get older, but in a managed way now."

The Penickovas, whose parents are from Czechia and both played pro tennis, are relentlessly positive in recent interviews, and why shouldn’t they be after the seasons they have had.

Kristina Penickova, the No. 9 seed in the Girls' tournament, made the semi-finals at Roland Garros and has had strong results throughout 2024, making an appearance in the women’s qualifying draw here after being given a wild card.

Annika, unseeded in New York, scored a strong first-round upset over No. 12 seed Antonia Vergara Rivera of Chile.

Both Annika and Kristina won second-round singles matches on Monday, with the result being the farthest Annika has gone in a Slam this year.

“To have my first wins here, over such good players, is incredible,” Annika said. “This is only our second time (at the Open), so everything is just amazing and I feel so lucky to be here.”

The Penickovas have been moving up so far, so fast, and Kristina said having a sister going through the exact same thing has been a blessing.

“It’s a huge help, to have a buddy with you who you trust completely with everything,” Kristina said. "We both want the same thing, and we help each other out, and it makes it so much easier.”

The Penickovas do everything together, including play doubles, where their “twin-tuition” gives them an advantage like another twin sibling duo from California, the legendary Mike and Bob Bryan.

“I know where she’s going to be and she’s always knowing where I’m going to be,” Annika said.

For Olga and Tomas, seeing the girls play together in doubles is blissful. But when they’re on the same side of the draw at tournaments and have to face each other?

“I don’t think they can even watch; I know my Dad (who also helps coach them) doesn’t like to watch,” Kristina said. “We never really look at the draw, honestly if it happens, it happens, and we try not to worry about it.”

Asked to name a trait of the other's that people wouldn’t know about, each Penickova thinks for a minute. Annika said Kristina often is half-asleep and snoring while talking in her sleep, and when Annika tries to wake her “she smacks me away and is mad that I woke her.”

Kristina counters that her twin “is really territorial. Like, a lot of sisters share clothes and stuff, but she’s always like ‘no, that’s mine'.”

Still, there is clearly much love between them, and the idea of turning pro in a few years excites them.

Tom Gutteridge, one of their coaches, said he’s seen a big improvement in 2024.

“They’re getting better at getting out of the corners, and transitioning from defense to offense,” Gutteridge said. “Their physicality, their movement … there’s still a long way to go, but they’re great girls and very easy to coach.”

For Kristina and Annika, winning a Grand Slam in their home country, in either singles or doubles, would be a lifetime thrill.

But they’re mature enough to know that the long game is what matters.

“Obviously we want to win everything we play, but we know it’s about getting better all the time,” Kristina said. “We want to play pro tennis and play Coco (Gauff) and win Grand Slams, but right now we’re just enjoying everything we’re doing, and feel lucky to get to do it.”

There was one big almost-upset in the Girls tournament Monday, as No. 1 seed Emerson Jones of Australia, a two-time Slam finalist this year, survived a challenge from Alena Kovackova but hung on, winning 5-7, 6-2, 7-5.