The Thulsie Twins entered into a plea and sentence agreement with the state, during the first day of their trial at the High Court in Johannesburg.
The brothers are facing charges for plotting alleged terror-related attacks on South African soil.
Tony-Lee and Brandon-Lee Thulsie were arrested in 2016 following raids in various parts of Gauteng.
They are also accused of having links to the Islamic State and for plotting to carry out attacks on the US embassy.
The brothers have been denied bail twice and have been incarcerated for over five years, awaiting trial.
DISCUSSION: Thulsie twins facing charges for plotting attacks on South African soil
THE STATE VS THULSIE TWINS