The English King Edward IV, forgave his brother George for one act of treason. George continued plotting though and the second time his brother was not so forgiving. He made George get off the planet.

Fredo put Michael in an impossible position.

"When the snows fall and the white winds blow, the lone wolf dies but the pack survives."
Winter is Coming

Now this is the Law of the Jungle—as old and as true as the sky; And the wolf that shall keep it may prosper, but the wolf that shall break it must die.
As the creeper that girdles the tree-trunk, the Law runneth forward and back; For the strength of the Pack is the Wolf, and the strength of the Wolf is the Pack.