if we look at this from the stand point of 'the rivalry of a father and son over a woman...' this can bring out soo many questions...

jack and his dad competing for sarah is the first that comes to mind...
but what if the same thing happened between locke and his father over helen??
the competion over kate between jack and sawyer??

will there be other competitions for affection between the islanders??? desmond and charlie over claire for example??? some say locke has an interest in claire that makes charlie jealous...

with rivalries avariety of emotions can be explored... love, hate, jealousy, possesiveness, freedom, caring, support.... and the compromise that couples make can be shown as it has with rose and bernard....

then again, the rivalries could just be another red herring given to us to distract us from the real thing.... because love can be such a detractor to life....