They now say the attacks on July 15 and July 25 are connected.
Tamisha Thompson and Denshawn Thompson are both 20 years old. It is unclear how or if they are related according to police. They've both been charged with numerous crimes, including armed robbery.
Authorities say they were armed with a knife and gun during the robberies.
Neither person is in custody.
"These charges are a result of aggressive investigatory work and the assistance of the community, Durham Police and other agencies," said John Dailey, chief of Duke Police. "We never want these crimes to occur and appreciate the excellent work that has gone into these cases."
Anyone with information regarding the suspects' whereabouts should call 911 or CrimeStoppers at (919) 683-1200.