By Colleen Kratofil
Updated January 31, 2016 02:16 AM

Rooney and Kate Mara may have the market cornered on “best-dressed sister act” in Hollywood, each managing to out do one another with their couture confections. But as in many cases, they’re even stronger together than apart, as proved by their jaw-dropping entrance at the Screen Actors Guild Awards wearing sexy, plunging Valentino gowns.

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Both Mara sisters went for deep cleavage-baring designs, with Kate in a beige halter gown with sexy side cutouts (and Forevermark diamonds) and Rooney in a V-neck pleated Haute Couture gown paired with a cropped cape and Fred Leighton jewels. But to hear Rooney tell it, it was “an accident” that they both chose the same designer.

And though her plunge was one of the lowest of the night, “I don’t know if this is sexy by most people’s standards,” Rooney said, “but for me it’s more revealing than normal.”

Despite bringing the drama, the Mara sisters (who clarified that it’s technically May-ra, for those looking to pronounce it correctly) dished that their normal wardrobe attire is the exact opposite. “I’m definitely in sweats,” Rooney said. “I rarely get dressed it’s really bad. In L.A. you never put real clothes on.”

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Which was evident in Kate’s description of their pre-SAG Awards night: “I walked into the house and she [Rooney] was in a robe with her feet in the jacuzzi. And then I opened the Champagne. But I drank a lot of it. A lot for me is a couple glasses.”

For Rooney? “I had, like, a few sips.”

Rooney previously told PEOPLE she regularly relies on her older sister for makeup tips. “I am horrible at putting on makeup,” Rooney said. “[Kate] has tried to help me in that department because she is really good at it. But I am still pretty hopeless.”

With a few more award shows to go (Rooney’s nominated for Best Supporting Actress at the 2016 Academy Awards) we hope there are more matching moments to come!

What do you think of their sexy gowns? Share with us in the comments below!

— Colleen Kratofil