A rupture in the relationship of the two brothers is quite apparent.

Gap : a break or hole in an object or between two objects.
Damage : physical harm that impairs the value, usefulness, or normal function of something.
Join : link; connect.
Breach : make a gap in and break through (a wall, barrier, or defence).
Rupture : (especially of a pipe or container, or bodily part such as an organ or membrane) break or burst suddenly.

Synonym of is breach