French investigators have charged the daughter and the son-in-law of Congo's President Denis Sassou Nguesso with corruption, judicial sources told AFP on Sunday.
Julienne Sassou Nguesso and her husband Guy Johnson were placed under investigation this week for "money laundering and misuse of public funds", the sources said.
Already in March, the nephew of the Congo-Brazzaville president, Mr Wilfrid Nguesso, was placed under investigation on the same counts.
The development is part of a series of inquiries by the French authorities into the assets of three African presidential families that began in 2010.
French investigators have been looking into the entire Nguesso clan as well as relatives of Gabon's late President Omar Bongo and his son, the current ruler, and President Teodoro Obiang' Nguema of Equatorial Guinea.
President Obiang''s son, Teodorin, is currently fighting a case in a Paris court for having pillaged the country's assets to fund a lavish personal lifestyle.
The trial sets a precedent for France which has long turned a blind eye to African dictators parking ill-gotten gains in Parisian real estate and luxury products.
The trial came about after nearly a decade of lobbying by activist groups Sherpa and Transparency International.