Demi Moore, 61, and Her 3 Daughters Show Off Their Bikini Bodies While Celebrating Scout Willis' 33rd Birthday: Photos

Scout Willis' 33rd birthday was a family affair!

To celebrate another year around the sun, the actress was joined by friends, her sisters and their mom, Demi Moore, for a day of fun at the lake.

Scout's older sister, Rumer Willis, 35, shared photos from the outing, where the birthday girl rocked a yellow string bikini alongside sibling Tallulah Willis, 30, who also wore a two-piece swimsuit.

Rumer — who brought along her and boyfriend Richard Derek Thomas' daughter, Louetta, flaunted her figure in a pale yellow one-piece, while the mother-of-three — who welcomed her daughters with ex-husband Bruce Willis — showed off her fab figure in a white bikini.

"River Monsters for @scoutlaruewillis birthday," Rumer captioned the Saturday, July 20, Instagram upload. "No place I would rather be than by your side."

The matriarch also paid tribute to the birthday girl, gushing on Instagram, "My sweet angel @scoutlaruewillis. Happy Happy Birthday!"

"I am so privileged to be your mother and so grateful to be sharing this journey of life with you!" continued Demi. "The best is yet to come and I am so excited to see the magic that unfolds for you! I love you!"

Tallulah also honored her big sis on her special day by posting a video of them singing in the car together.

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Scout herself marked the occasion on social media by posting a selfie.

"I AM 33! IT’S MY BIRTHDAY! MY JESUS YEAR BEGINS! I AM SO HAPPY! I AM SO LUCKY! I FEEL SO GRATEFUL!" she raved. "I REALLY LIKE MYSELF AND I LOVE WHO I BECOME EVERY DAY! I LOVE MY LIFE! I FEEL SO INSPIRED AND THIS IS GOING TO BE THE BEST YEAR OF MY LIFE SO FAR!"

As OK! reported, the Willis girls and the St. Elmo's Fire star have been spending a lot of time with Bruce, 69 — as well as his wife, Emma Heming Willis, 46, and their two daughters — after he was diagnosed with frontotemporal dementia last year and aphasia the year prior.

Though the disease has taken a toll on the action star's verbal skills, Rumer said in May that the dad-of-five was doing "really good."

The House Bunny actress told the reporter that the outpouring of love their blended family has received in the wake of the Sixth Sense lead's diagnosis made her realize just how "beloved" her father is.

"I feel like that’s been so evident in the transparency with which we’ve been sharing," she said. "If sharing our experience, strength, hope and whatever comes forward as a family, if that can bring any sort of hope or comfort to someone else who’s experiencing that, then to me that’s everything."