Carl then recounts, "When I was 13 years old I had some close friends in a Zionist youth group called Betar. They wore uniforms and kept talking about a Jewish state on both sides of the Jordan. I didn't care about that. I just wanted to be with Shloime and Moishe."
Source
P.S. Okay, who was his madrich?
UPDATE
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Both Marty Marden and Seymore Rosenberg, z'l, knew Carl Reiner when he was in Betar in the Bronx ken. They often talked about him. I think he must have been older than 13, which would have been 1933 if he is now 86. I would guess that it was later in the 1930's.
Ray Kaplan