Sammy was the brother of Cinder. He was killed along with his parents when the Daleks invaded their home planet of Moldox near the close the Last Great Time War.
Sammy once made a bracelet for Cinder. Years later, she broke the bracelet to use as a lockpick so she and the War Doctor could escape a Time Lord prison cell on Gallifrey. She apologised to her dead brother before she did this.
After the Doctor defeated the Daleks occupying Moldox, he dug up the skeletal remains of Sammy and his parents and buried them at the location of their old homestead along with Cinder, who died helping him defeat the Daleks. (PROSE: Engines of War)