Mars in H12 by itself is not impossible but in this case it has no positive aspects to help. I just looked in the Rob hand Planet sin Composite book and here are some of his comments:
" it is absolutely imperative that the two of you understand exactly what you want from this relationship...you are putting into the relationship it will be difficult to ascertain why you sources of conflict that could weaken it... unconscious forms of ego expressions.. make demands explicit...might be very profitable to write out an agreement..."
Mars square Saturn in a composite often signals differences in timing, or significant age differences.
The Moon in this Composite is very strong, but the Sun is weak with no really good aspects except a conjunction to Mercury, and in fact the Sun is opposite Uranus which suggests the opposite of stability or longevity but will likely be unconventional and unpredictable.
Have you done a synastry chart?
Barb at thelivingsky.wordpress.com