Seymour, 62, and Keach, 65, had been married 20 years. Documents filed by Seymour last week in Los Angeles County Superior Court cited irreconcilable differences.
The former couple released a joint statement in April to announce their separation.
"Jane Seymour and James Keach confirm that they are separated and have been for several months. At this time they are negotiating the terms of their divorce," the couple said in the statement.
The two share two sons, 17-year-old twins Kristopher and John. Seymour requested joint legal and physical custody but did not request spousal support.
"They will continue their relationship as devoted parents to their children, as business associates and partners, and in their joint dedication to preserving and furthering the charitable endeavors that they've worked on throughout their marriage."
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