who played andy's brother in the office
Josh Groban.
Garden Party (The Office)
 Andy is jealous at the amount of attention his younger brother Walter Bernard, Jr. (Josh Groban) receives from his father, and thinks that by throwing an elaborate party he can ensure his father's blessings. 
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Garden Party (The Office) [SEP] Synopsis
Andy Bernard (Ed Helms) decides to throw a garden party at Schrute Farms to impress his parents and Robert California (James Spader), and exhaustively explains party manners to the office workers. Andy is jealous at the amount of attention his younger brother Walter Bernard, Jr. (Josh Groban) receives from his father, and thinks that by throwing an elaborate party he can ensure his father's blessings. At first, the party goes along smoothly. Andy makes a toast to Robert in order to get his fellow employees to toast him, as if to show to his parents and California that he is valued by his employees.