Question: What apartheid system opponent is the father of screenwriter Shawn Slovo?

Context articles: Catch a Fire (film)
Marthinus Versfeld
South African apartheid referendum, 1992
Disinvestment from South Africa
Joe Slovo
Shawn Slovo
A World Apart (film)
United Nations Security Council Resolution 569
Inequality in post-apartheid South Africa
Kaffir Boy

Catch a Fire is a 2006 biographical thriller film about activists against apartheid in South Africa.
 The film was directed by Phillip Noyce, from a screenplay written by Shawn Slovo.
 Slovo's father, Joe Slovo, and mother Ruth First, leaders of the South African Communist Party and activists in the Anti-Apartheid Movement, appear as characters in the film, while her sister, Robyn Slovo, is one of the film's producers and also plays their mother Ruth First.
 "Catch a Fire" was shot on location in South Africa, Swaziland and Mozambique.
Marthinus Versfeld (or Martin Versfeld) (11 August 1909 – 18 April 1995) was a South African philosopher.
 From 1937 to 1972 he taught at the University of Cape Town.
 He was celebrated as researcher, enjoyed the recognition of the South African literary community and was known as an opponent of the Apartheid system.
 His work ranged from scholarly books to playful essays on issues like ethics, anthropology, the meaning of life.
A referendum on ending apartheid was held in South Africa on 17 March 1992.
 The referendum was limited to white South African voters, who were asked whether or not they supported the negotiated reforms begun by State President F. W. de Klerk two years earlier, in which he proposed to end the apartheid system that had been implemented since 1948.
 The result of the election was a large victory for the "yes" side, which ultimately resulted in apartheid being lifted.
Disinvestment (or divestment) from South Africa was first advocated in the 1960s, in protest of South Africa's system of apartheid, but was not implemented on a significant scale until the mid-1980s.
 The disinvestment campaign, after being realized in federal legislation enacted in 1986 by the United States, is credited by some as pressuring the South African Government to embark on negotiations ultimately leading to the dismantling of the Apartheid system.
Joe Slovo (born Yossel Mashel Slovo; 23 May 1926 – 6 January 1995) was a South African politician, an opponent of the apartheid system.
 He was a long-time leader of the South African Communist Party (SACP), a leading member of the African National Congress (ANC), and a commander of the ANC's military wing Umkhonto we Sizwe.
Shawn Slovo (born 1950) is a screenwriter, best known for the film "A World Apart", based on her childhood in South Africa under apartheid.
 She is the daughter of South African Communist Party leaders Joe Slovo and Ruth First.
 She wrote the screenplay for the 2006 film "Catch a Fire" (also a historical film about apartheid), and for the 2001 film "Captain Corelli's Mandolin".
A World Apart is a 1988 anti-Apartheid drama, written by Shawn Slovo and directed by Chris Menges.
 It is based on the lives of Slovo's parents, Ruth First and Joe Slovo.
 The film was a co-production between companies from the UK and Zimbabwe, where the movie was filmed.
 It features Hans Zimmer's first non-collaborative film score.
United Nations Security Council resolution 568, adopted on 26 July 1985, after expressing its outrage and concern at the suffering caused by the apartheid system in South Africa, the Council further condemned the repressive policies of the apartheid system including murders and forced removals, as well as the state of emergency imposed in 36 districts in the country, demanding it be lifted immediately.
President Nelson Mandela's democratic election in 1994 marked the end of apartheid in South Africa,  a system of widespread racially based segregation to enforce almost complete separation of the different races in South Africa.
 Under the apartheid, South Africans were classified into four different races: white, black, coloured, and Indian/Asian, with about 80% of the South African population classified as black, 9% as white, 9% as coloured, and 2% as Indian/Asian.
 Under apartheid, whites held almost all political power in South Africa, with other races almost completely marginalized.
 While the end of apartheid enabled the nation to maintain full legal equality of all South Africans, regardless of race, today’s South Africa struggles to correct the social inequalities created by decades of apartheid.
 Despite a rising GDP, indices for poverty, unemployment, income inequality, life expectancy, land ownership, have declined due to the increase in population, with the end of the apartheid system in South Africa leaving the country socio-economically stratified by race.
 Subsequent government policies have sought to correct inequity with varying amounts of success.
Kaffir Boy: The True Story of a Black Youth's Coming of Age in Apartheid South Africa is Mark Mathabane's 1986 autobiography about life under the South African apartheid regime.
 It focuses on the brutality of the apartheid system and how he escaped from it, and from the township Alexandra, to become a well-known tennis player.