Dube was assassinated by two attackers in Lamontville outside Durban in April 1983.
His younger sister, Daphney Mnguni, will recount events which led to his murder, Truth Commission spokesman Mdu Lembede said in a statement.
Relatives of Turner, a University of Natal political scientist, will also testify about his murder.
Turner was gunned down in front of his two daughters in his Overport home in January 1987.
His first wife, Barbara Follett, who is a Labour Party politician in the United Kingdom, his second wife Foszia, and daughters Kim and Jann will testify, Lembede said.
Durban sociologist Prof Fatima Meer and Harold Strachan, a founder member of the African National Congress' armed wing Umkhonto we Sizwe, will also appear before the Truth Commission on Thursday.
The first commission hearings set aside exclusively for women will be held in Durban on Friday.
A panel of commissioners comprising women only will hear evidence from women. Men will not be allowed to attend.
Both hearings will be held in the Durban Christian Centre.