The FDLR are one of the most feared militia groups in Congo.
Their leaders fled into the forests from Rwanda in 1994 after taking part in the genocide and have plagued the east of the country ever since.
Their notoriety has reached such heights that last year the UN joined the Congolese and Rwandan Armies in a lengthy offensive against them.
In the second of his reports from the nation's troubled east, correspondent Mike Thomson talks to a former child soldier who has spent nearly half his life in the forest with FDLR rebels.
This extended interview contains descriptions of violence which some may find disturbing.
Save the Children estimates there are up to 250,000 children held by armed groups around the world, thousands of them in DR Congo.
Organisations working with child soldiers in DR Congo include: