The two met when Garces Williams worked as a nanny for Williams' son Zachary, whom he had with his previous wife, Valerie Valardi.
Robin and Garces Williams also have two children together, Zelda and Cody.
Williams, 56, won an Academy Award for his role in the film "Good Will Hunting." He also starred in the 1980s sitcom "Mork & Mindy," and has acted in a number of movies including "Dead Poets Society" and "Patch Adams."
Williams' agent Mara Buxbaum confirmed that the couple is splitting, but had no further comment. An attorney for his estranged wife would not comment on the case.