Josh Robertson and Brittney Humphrey were extradited last week and put in Los Angeles County jails.
Both were in court for their arraignment on Tuesday, September 27 and the arraignments will continue next month.
Humphrey is being held on $2 million bail, while Robertson is being held on $3 million bail.
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The two were originally arrested in Colorado for their connection with the kidnapping of three young children whose mother's body was found in the Gorman area in early August.
They were last seen with Kimberly Harvill's three children and fled California in Harvill's green 1999 Ford Expedition.
Harvill's body was found lying in brush in a remote area north of State Route 138 by a motorist on August 14.