They are soul forged, as such one can not exist without the other. They can't be separated too much from eachother and when the one dies so does the other.
That will keep them fighting together and not eachother.
The question is a valid one though. The assumption can be made that in the end the soul forge wil be separated. What happens then? Maybe they become friends and live happily ever after <img src="/ubbthreads/images/graemlins/biggrin.gif" alt="" />
