David and Angela Cook of Cleburne were arrested Monday, the Fort Worth Star-Telegram reported. Bail was set at $75,000 each.
Buddy Cook died March 22. Child Protective Services said he weighed 37 pounds, about 6 pounds underweight for his age, and appeared to suffer from both malnutrition and dehydration.
The charges filed so far allege the Cooks should have gotten medical care for the boy. The Tarrant County Medical Examiner has not ruled on the cause of Buddy's death.
The Cooks say Buddy was conceived through incest and had been abused by his biological mother and several men, causing him to have severe emotional problems.
The couple had seven other children in their home, who have been placed in foster care.