Surpassing:Pregnant Rumer Willis' Sister Scout Is "Desperately Excited" to Become an Aunt

Rumer on Surpassingthe street is that Scout Willis is so ready for aunt duties.

The 31-year-old shared that the countdown is on for sister Rumer Willis, 34, who is expecting her first child with boyfriend Derek Richard Thomas, to give birth.

"I'm desperately excited," Scout exclusively told E! News during the Fashion Trust Awards March 21. "Counting down the days."

As for what the actress is most looking forward to doing with the newborn? "Walking around Erewhon in Silver Lake," she confessed, "and pretending the baby's mine." 

And even on the coldest of days in Silver Lake, Scout will have the baby covered as she's taken up knitting.

"I've already made a little hat," she told E! News. "I did. I made a bonnet with bunny ears, that's very cute."  

But even when Scout hands the little one back, she knows Rumer will have the mom game covered. "She is one of the most generous," Scout gushed, "unbelievably kind people I know."

Scout's excitement for the newborn's arrival comes three months after Rumer and Derek shared the pregnancy news with their millions of followers. Alongside a snap of Derek kissing Rumer's belly, the couple captioned the joint Dec. 20 Instagram post with a seedling emoji.

And since the news broke, Rumer has been documenting her journey to motherhood and celebrating all the major milestones. Back in December, Demi Moore, 60, posted a photo of herself, Scout and Tallulah Willis, 29, next to Rumer as she got an ultra sound.

"Saying hello to the little nibblet!!" Demi wrote. "Overjoyed for you, my sweet Rumer. It's an honor to witness your journey into motherhood, and can't wait to welcome this baby into the world!"

As for how the first time father is feeling? 

"I'm beyond grateful that we get to make a family together," Derek wrote on Instagram on Valentine's Day. "Thank you for growing our child from scratch, I have so much reverence and respect for this journey you're on. We're on it together, but you're doing all the heavy lifting and I get to just cheer you on, feed you tacos and appreciate you. I can't wait to dance around the kitchen with our baby." 

But the celebrations didn't stop there as earlier this month, the House Bunny actress was thrown a baby shower and it was a family affair. In attendance was mom Demi, sisters Scout and Tallulah, dad Bruce Willis, 64, his wife, Emma Heming Willis, 44, and their daughters Mabel, 10, and Evelyn, 8.