His father, Felix, was born on 24 November 1919 in Steynsburg, in the Free State. Playing at lock, Felix made his debut for South Africa on 16 July 1949 at Newlands Stadium, Cape Town against the touring All Blacks, led by Fred Allen. His team – which included Springbok greats Tjol Lategan, Hannes Brewis, Okey Geffin, and Hennie Muller – swept the series 3 – 0. Six weeks after the last test, Morné was born. Felix worked as a representative for South African Breweries, then relocated to Vereeniging to manage Iscor's sport and recreation department. He moved to Stilfontein, where he opened a liquor store, one of the first shops in town. Morné recalls his father as a gentle and retiring person, who only started watching his son play rugby once he was at Stellenbosch. Felix Du Plessis died at Stilfontein in 1978 at the age of 58, having played only the three tests against New Zealand.