Demi Moore, Ashton Kutcher Help Rumer Willis Celebrate 21st Birthday

Rumer Willis rang in her 21st birthday with family in friends in Sin City!

Rumer's birthday bash was held at TAO at The Venetian Las Vegas -- and the starlet was joined by her parents Demi Moore and Bruce Willis, her stepfather Ashton Kutcher, her boyfriend Micah Alberti, and her younger sisters Tallulah and Scout.

Also in tow for the celebration was Rumer's 'Sorority Row' co-star Audrina Patridge, and pals Holly Madison, and Soleil Moon Frye.