From The Stargate Omnipedia
German associate to Dr. Langford in 1945. During the height of the Second World War, when President Roosevelt was searching for new forms of weaponry against the enemies of the United States, he pressed Dr. Langford's team to discover the mysteries of a great ring.
At the time Gruber was well acquainted with Langford and knew of his daughter, Catherine.
It is doubtful that Gruber had a son, though Dr. Daniel Jackson posed as one in 1969 to gain Catherine's confidence in accessing the Stargate while it was locked away in a Washington D.C. armory.
1969 - Catherine Langford welcomes Heinrich Gruber's "son" into her home, never aware her father's assistant had one.