A woman and her daughter are facing incest charges after authorities learned they legally married in Oklahoma this year.

The motivation behind the marriage was unclear Wednesday, when 43-year-old Patricia Ann Spann and 25-year-old Misty Velvet Dawn Spann made initial court appearances. Under Oklahoma law, marrying a close relative is considered incest whether or not a sexual relationship exists.

According to a police affidavit, officers learned about the marriage last month amid a child welfare investigation. Patricia Spann allegedly said she'd lost custody of three children, but reunited with her daughter two years ago.

Detectives later learned she married her son in 2008. He filed for an annulment 15 months later, citing "incest."

Court documents don't list attorneys for either woman. No phone number is listed for their Duncan home.