 In 1998, Piet Koornhof and his son, Gerhard Koornhof, until then members of the National Party, announced that they were joining a new multiracial party, the United Democratic Movement of Bantu Holomisa.In 2001, he joined the African National Congress.On several occasions Koornhof's marital problems came to the fore, especially during his 12-year separation from his wife, during which he lived together with his girlfriend.