Ndambi Guebuza, son of former President Armando Guebuza, and the others face charges of blackmail, embezzlement and money laundering.
They have not yet commented on the charges.
Mozambique's biggest corruption scandal led donors including the IMF to cut funding for the country and the economy to collapse.
The trial is being held in a large canvas tent in the grounds of a maximum-security prison in the outskirts of the capital, Maputo.
