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Gillian Anderson is sadly adding longtime love Mark Griffiths to her ex files.

"Gillian Anderson and her partner Mark Griffiths have amicably separated after six years together," a rep for the actress, 43, tells Us Weekly exclusively.

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The duo, who never wed, share sons Oscar, 5, and Felix, 3.

The "X-Files" and "House of Mirth" actress has been married twice before. She and film art director Clyde Kotz, with whom she shares daughter Piper, 17, divorced in 1997; the star and documentarian Julian Ozanne were married for two years before parting ways in 2006.

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Following her role as Miss Havisham in a 2011 PBS miniseries adaptation of "Great Expectations," Anderson has a full slate of projects in 2012: the films "Mr. Morgan's Last Love," "I'll Follow You Down" and "The Curse of the Buxom Strumpet," plus BBC miniseries "The Fall."

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