Kaley Cuoco, Briana Cuoco Are “Best Friends,” “Could Not Have Been Nicer” on The Voice Set

Briana and Kaley Cuoco on July 24, 2013
Kaley Cuoco and her best friend and younger sister, Briana Cuoco, "could not have been nicer" on The Voice, a source tells Us Weekly Michael Kovac/WireImag.com

Kaley and Briana Cuoco are one classy sister act. The Big Bang Theory actress, 27, and her younger sibling and personal assistant — a contestant on the new season of The Voice — are the talk of the town in Hollywood these days, and it's not hard to see why. 

PHOTOS: Vote for the hotter star sibling!

"Briana is super cool and really down to earth," a source tells Us Weekly of the aspiring singer and actress. "She never demanded any special treatment or anything like that on set."

Her sister, who ecstatically cheered on Briana from backstage, sounds similarly awesome. "Kaley and Briana could not have been nicer," the source says. "They are incredibly close and supportive of one another. You can tell they are best friends."

Indeed, Kaley gushed on Monday's episode of The Voice that she's Briana's biggest fan. "I've been waiting for something like this for so long for her," the CBS star said. "She's deserved this her whole life and she's always put herself on the back burner for everyone else…There's no one I love more in the world. My sister and I are closer than close. I want this for her probably more than she maybe wants it."

Briana, for her part, is equally effusive about Kaley — though she admits there are some challenges in having a famous sister. In a conference call with reporters, she said people assume she has "an in" just because Kaley is "successful in one field in the business." But that's not necessarily the case. "People open doors all the time for people…but you have to be the one to close them, no matter what," she explained.

"I am incredibly lucky to have [Kaley] and to have her support and to have been around the business for a long time. So I have that on my side, absolutely," she continued. "But on the other side, I do have…more pressure on me. I think people expect a little bit more because of that, which is a great thing because it keeps me driven. But it also can be a little harder sometimes when people are a little extra critical in certain cases."

Fortunately, Briana's experience on The Voice thus far has been pretty positive. "It was such a beautiful thing having [Kaley] there with me and truly mentoring me," she gushed, noting that her whole family had been really encouraging. "My parents have been incredibly supportive of my sister and my career, and to have all of them there and her supporting me — it was amazing. It was truly one of the best moments of my life."

The Voice airs on NBC on Mondays at 8 p.m. ET, and on Tuesdays at 9 p.m. ET.

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