He is vice-president to his father, Teodoro Obiang Nguema, who has ruled Equatorial Guinea for 40 years.
Twenty-five of Mr Obiang’s cars are going under the hammer at a golf club near Geneva.
A Lamborghini Veneno Roadster, valued at up to $6.2m, and an Aston Martin One-77 Coupe, valued at up to $1.7m, have been described as “rare and remarkable”.
The cars, which do not have a minimum reserve price, have attracted interest from collectors across the world, especially Europe, Ms Farrant said.
The proceeds of the sales will be donated to a charity in Equatorial Guinea, a former Spanish colony where poverty is rife.
In total, 75 cars are being sold at the auction in the Swiss village of Cheserex, 30km (18 miles) from Geneva.
Who is Teodorin Nguema Obiang?
Mr Obiang is seen as the heir-apparent to his father, who has been president since 1979.
In international media reports, Mr Obiang has drawn criticism for his extravagant spending habits and playboy lifestyle.
In a 2004 article, the New York Times described him as “a rap music entrepreneur and bon vivant, fond of Lamborghinis and long trips to Hollywood and Rio de Janeiro”.
Swiss prosecutors were investigating Mr Obiang for money laundering and misuse of public funds, but dropped the case in February this year.
In 2017, a French court handed him a three-year suspended jail term for corruption.