On Monday, officers arrested 26-year-old Ezequiel Gonzalez in connection with the death investigation.
In November, Deysi Yhuriko Martinez was arrested after her son died of internal injuries.
Officers said Martinez was accused of not getting him medical treatment in a timely manner.
The incident happened in August at an extended stay hotel on Hwy 70 in Garner.
During a first court appearance, a prosecutor said the child died just days short of his 4th birthday after suffering an intestinal tear.
"Wake Medical Center was unable to successfully repair the tear to his intestines. It had caused sepsis and the infection is what killed him," said Wake County Assistant District Attorney Melanie Shakita. "The state's position is that had she sought medical care for her child that he likely would not have died."
READ MORE: Wake County mother charged after 3-year-old child dies
"It had to be obvious that this child had some kind of internal injuries and the parents should have known. The mother should have known that that child needed emergency care and she didn't provide that in a timely manner," Capt. Joe Binns with the Garner Police Department told ABC11.
Detectives are still working to learn how the boy was injured.