Well, to make a long story short, The Warner Brothers were Jewish!
Since The Warner Brothers's mother was Jewish, and in Orthodox Judaism and Conservative Judaism, those with a Jewish mother (or those who underwent a halakhic conversion) are considered Jewish, then that makes them Jewish. Their father was Jewish too.
The Warner Brothers were born on 1881 (Harry Morris Warner), 1884 (Aaron ''Albert'' Warner), 1887 (Samuel Louis ''Sam'' Warner) and 1892 (Jack Leonard ''J. L.'' Warner) in Poland and Canada.
They are the founders of Warner Bros. Entertainment Inc. (commonly referred to as Warner Bros.), which is the world's largest film and television studio.
If you see any details that require update, please Let us know!