Three were Jews, three were not. Hitler broke up the group, I forget when, 1934 or 1935. All six survived the war but they never got together again, and never really got friendly again. The last died only a few years ago, in Palm Springs, CA.
The Harmonist were inspired to get together in the first place by an American group of the 1920s, I think called The Revellers -- a sophisticated group described as barbershop with a college degree. I have a couple of things they did on Retro CDs, "My Blue Heaven" and one other I can't think of.
I have a few Revellers recordings, including a beautiful rendition of Yankee Rose, a hit from 1927, on 78. As a graduate of Whittier High School in Whittier, Calif.--where Richard Nixon was once a student, and First Lady Pat Nixon was once a teacher--I am especially interested in Yankee Rose, because our school's alma mater uses that tune. When I was in the band, and we played the tune at the conclusion of football games, I had to play the tuba part on the baritone horn, because there was no baritone part.
Here's a version of Yankee Rose that was heard at the Republican National Convention in 1928:
Oh, Hoover's name and Hoover's fame
Are known at home, and around the world the same.
Our nation calls, he's the best of all.
He is tried and true. We know he'll do.
And he'll be elected president next fall.