Twins Mary-Kate and Ashley olsen have just celebrated their 21st birthday and unlike many young stars hitting the milestone, they kept their celebration low-key. The sisters hosted a small dinner with family and friends at the Chateau oarmont in Hollywood. After the dinner each guest took turns at raising their glass and saying a few words about the girls. An onlooker tells, “You could tell they were all really close. The girls couldn’t stop smiling.”