Mordekhai Grinberg was born in Siemiatycze, Poland, 1920 to Avraham. He was single. Prior to WWII he lived in Siemiatycze, Poland. During the war he was in Forest, Poland. Mordekhai survived the Shoah.
Jews deported to or imprisoned in camps, ghettos or forced labor frameworks, who were in hiding, in clandestinity or resistance formations, or suffered relentless persecution under antisemitic legislation in territories controlled by the Nazis or their allies, and were alive by the end of 1945 are considered Shoah survivors.