Kardashians’ Super-Sexy Mexican Getaway!

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Itsy-Bitsy Yellow Bikini!

"She totally firmed up!" Kourtney's trainer David Barton tells Us of her incredible beach bod (shown off in a Mikoh two-piece).

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Mommy 'n Me

"Mason didn't like the beach, but he really enjoyed the pool," says a witness of Mason.

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Beach Goddess!

"Yes, Kim and Kourtney worked out every day of their vacation!" a source tells Us of Kim, 30, and her sister.

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Pucker Up!

Kris Humphries, 27, made his famous love unplug her phone for the 6-day getaway. "He's amazed she held to it!" a source says.

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With Aunt Kim and Uncle Kris!

The gang were guests at the oceanside compound of longtime pal Joe Francis of Girls Gone Wild fame. "We go [there] every year with friends and family," Kim tells Us.

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The Gang's All Here!

Scott, Kim, Kris, Rob and other pals got some snacks at a local shop.

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Mason's Mile-Wide Smile!

Kourtney and her baby boy have a sweet moment.

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Wet and Wild!

"They were splashing each other," a witness says of Kim (wearing a Beach Bunny bikini) and beau Humphries. "Kim tried running away, but he caught her!"

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I Got You, Babe

"Kim tried running away, but he caught her!"

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Double Beach Date

After a party for birthday gal Kourtney on the night of their arrival -- complete with cake and mariachi band! -- the couples kept it low-key for the 6-day stay. "It was a really romantic getaway," a source says.

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Head and Shoulders Above

"Kim was excited to get some alone time with Kris," an insider says. "They were making out the whole time!"

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Little Guy's Moment in the Sun

"Mason was having a ball," a witness tells Us. And his parents "were so in love...It was sweet!"

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Hot Pink!

"She is fierce!" trainer Tracy Anderson says of the 5-foot-2 Kim's workout.