The most common form of abduction is defined as "the taking or keepings of a child by a family member in violation of a custody order, a decree, or other legitimate custodial rights."
The BAU doesn't typically handle such matters but they stumbled upon Sera Morrison in Season 8. Originally investigating her father, the team turned their attention to his daughter after putting together the profile. Sera kidnapped and killed her little sister, as well as her mother in years prior, because she hated that her sister was the family "favorite." She tried to pin the murder on her father, who had dissociative identity disorder.
"All That Remains" (Episode 14, Season 8)