(idiomatic) while two dogs are fighting for bone, a third one runs away with it (when two people are involved in an issue, they might miss that the third party benefits from it)
In political disputes, one can often hear the saying 'when two people are fighting, a third benefits', which reminds us that conflicts do not always result in losses for everyone involved.
(idiomatic) Men are usually the dominant ones in a marriage, which is why they have to hit their wives into submission (usually used to justify violence against women)