Tallulah Willis Snaps Cute Pic Alongside Pregnant Sister Rumer Willis Showing Off Her Growing Baby Bump

Sister support! Tallulah Willis is making sure to be there for big sis Rumer Willis as she experiences the ups and downs of pregnancy.

One month after revealing she was expecting her first child, the actress posted a photo of her growing belly to her Instagram Story, with her younger sibling behind the camera of the mirror selfie.

"As soon as I found out I was pregnant one of the first things I did health-wise was start looking at what I was putting in my body, from food to lotions, oils, beverages and especially vitamins," the mom-to-be explained in her caption. "I wanted to find the most natural things I could with the fewest ingredients."

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After doing research and trying "a handful of prenatal vitamins," the 34-year-old found the perfect solution from the brand Shaklee.

Rumer and boyfriend Derek Richard Thomas received plenty of warm wishes when they announced their exciting news in December, with future grandma Demi Moore, 60, accompanying her daughter to one of her doctor's appointments.

"Saying hello to the little nibblet!! Overjoyed for you, my sweet Rumer," she wrote alongside an Instagram snap depicting the pregnant actress preparing for an ultrasound. "It’s an honor to witness your journey into motherhood, and can’t wait to welcome this baby into the world!"

Though Rumer's dad, Bruce Willis, 67, is battling aphasia — a cognitive disorder that prompted him to retire from acting this past March — a source said he's over the moon about the baby.

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"He is happy about becoming a grandpa. He loves having a big family," the insider shared. "Bruce is enjoying not working and having more family time."

Aside from the three daughters Bruce shares with Demi — they also have daughter Scout, 31 — he has daughters Mabel, 10, and Evelyn, 8, with wife Emma Heming, 44. The blended brood spent Christmas together and have vowed to gather as often as possible now that the Die Hard star's health is on the decline.

"The girls bring so much love, laughter and life into our home," Heming gushed in an interview. "For us as a family it’s always been about making memories. We just love spending time with each other and we know that time is precious, and I don’t take that for granted."