Mary-Kate Olsen and Olivier Sarkozy in the Hamptons. Credit: Patrick Mcmullan/Patrick McMullan/Sipa USA

Twin time! Mary-Kate and Ashley Olsen, who once filmed their mall parties, sleepover parties, and school dance parties, turned up in the Hamptons for a grown-up fête this past weekend with Mary-Kate's fiance Olivier Sarkozy in tow. 

The twins, 28, hit the posh Long Island vacation destination with Sarkozy, 45, on Saturday, Aug. 16 for the Paddle & Party for Pink benefit. The soiree was a rare appearance for Mary-Kate and her future husband, as the couple tends to stay out of the public eye. See more pics of Mary-Kate and Ashley at the party here.

Mary-Kate snuggled up to her banker love at the bash, which raised money for The Breast Cancer Research Foundation. Despite the warm summer weather, the younger of the Olsen twins by two minutes cloaked her slim figure in a pair of skinny jeans and a voluminous long-sleeved coat over a dark top. She wore minimal makeup and parted her blonde hair down the middle.

Sarkozy, who proposed to Mary-Kate this past February with a massive engagement ring after two years of dating, was summertime chic in a pair of navy pants, an unbuttoned pink collared shirt, and a blazer. 

The wife-to-be also posed for photos with her sister at the star-studded event, which was attended by Tracy Anderson, Martha Stewart, Bethenny Frankel, and Molly Sims, among others. 

Wearing a red-hued blazer over a black long-sleeved shirt and skinny jeans, Ashley hung out with designer Lisa Perry and Mary-Kate. While Mary-Kate attended the event with her man, Ashley was without her boyfriend Bennett Miller, 47, with whom she was seen in New York City earlier this month.