In a
relationship with two people, people see one
bond - the one between the two people. This bond is subject to all the
forces that can be placed on it. However,
no man is an island, nor is any relationship isolated from others. There are the mutual
friends,
co-workers, hangouts. Each relationship changes these bonds too, some slightly others more significantly.
When a relationship is broken, the other bonds are subject to stress. Mutual friends may take one side or the other, and not remain friends to the other party, other bonds may strain, and other bonds may go closer. Just as a rock thrown in a lake, these bonds forming and breaking cause ripples that radiate out.
As a sentient being that is capable of trying to predict these bonds and ripples, we are capable of looking before throwing the rock, and are responsible for all of the ripples that it may cause.