Uncontrolled jubilation washed over the sister of a former South African National Defence Force colonel who was imprisoned in South Sudan for more than two years.

"When I got the news I screamed [with] joy," Charmaine Endley Quinn told News24 on Wednesday evening.

Her brother, William Endley, was sentenced by a court in the capital city of Juba to jail following a peace deal gone wrong in 2016. He was reported the adviser of rebel leader Riek Machar, the former deputy president of South Sudan.

However, President Salva Kiir announced on Wednesday that Endley will be sent back to South Africa. This after Kiir and Machar came to a new peace deal in September that included the release of Endley.

"It has been two years and two months. It has been a very emotionally draining time for myself and my family. I never imagined this. It's like a dream come true. We are elated by the news and the commitment to the peace process," Endley Quinn said.

She said an advocate dealing with Endley's matter had "informed her" of the latest development.

"There are no final details yet. The advocate dealing with his case called me. There should be more details tomorrow. He could be released to the Red Cross. They normally do that for political prisoners."

Quinn said she and her brother have always been close.

"His military career took him all over the world, but we always stayed in touch daily. I never thought we would see the day something like this would happen."

She said that there were initial concerns for his safety.

"For a long time we did not know whether he was dead or alive. He is 57 years old and a grandfather. There were many harsh realities with his situation."

The latest peace deal that Endley is part off, is an attempt to end a five-year civil war that erupted in December 2013.