News24 quoted Hess's aunt as confirming that the arrested man was linked to her niece's murder - and that the man was a relative.
Hess, a University of the Western Cape theology student, and her 85-year-old grandfather, Chris Lategan, were found dead at home in Parow in September.
At the time, police spokesperson Lt-Col Andrè Traut said Hess, a youth leader, was found dead on a bed, while her grandfather was tied up in a toilet. A TV, cellphones and backpack were missing.
Van Wyk confirmed on Wednesday morning that the man whose photograph was shared on social media was “a person of interest” in the Hess case.
“Circumstantial evidence currently links him to the crimes,” he said.
Van Wyk said the man had also been positively linked to the alleged rape of a 16-year-old girl in Hanover Park on Monday.