The German-Moroccan brothers, aged 24 and 25, are accused of joining Isis as well as the al-Nusra Front terrorist group.
The older brother, Rachid B., reportedly travelled across Egypt and Turkey to Syria in February 2013 and initially joined al-Nusra Front. There he received shooting, combat and weapons training, and was given an assault rifle as well as ammunition. In April 2013, he helped capture a suspected spy, who was held for over a week.
By May of that year, Rachid B. left al-Nusra Front and joined Isis, keeping his assault rifle. With Isis he was trained in shooting and combat missions, and also held guard duty, according to prosecutors.
During this time he stayed in touch with his younger brother Khalid B. and advised him on which route to take to reach Syria.
Khalid B. reached Syria by July of 2013 from Germany and also joined Isis training.
Germany has been on high alert for terror given the attacks claimed by Isis in other Europeans countries, and the Christmas market truck attack in Berlin last month, also claimed by the terror group.