It is no secret inside Chabad about the Rebbe's 2 brothers. To use Barry Gurarie as proof is like quoting Bin Laden to prove America is evil. The "succession battle" was basically over before it began and very few of the insiders really considered Barry's father as Rebbe material. His grandmother had a hard time with it for various reasons, yet in her will she specifically requested that the Rebbe say kaddish for her.
Police disperse hundreds in brawl in Kafr Manda, northern Israel (Haaretz)
from the article: One brother became secular, the other was mentally ill