SAN FRANCISCO (Reuters) - Comedian Robin Williams‘ second wife, whom he met when she was his nanny, has filed for divorce citing irreconcilable differences, court documents showed on Wednesday.

Marsha Garces Williams filed her petition in a San Francisco court late last week. The couple has been separated since December 31, and she is requesting joint custody of their 16-year-old son, Cody, according to the filing.

The couple have been married since 1989 and have two children. Their daughter, Zelda, is 18 years old. They first met when she took care of Williams’ son with his previous wife, Valerie Valardi.

Williams, 56, rose to fame in the 1970s playing the wildly comic space alien Mork in the hit television show “Mork and Mindy,” and is known for his frantic, zany stand up comedy.

Garces Williams has worked as a producer on her husband’s films and co-owns their production company, Blue Wolf Productions. Her attorney, Robert Kaufman, was not immediately available to comment and Williams’ spokeswoman declined further comment.