Get your cat desexed. The other may be less inclined to come around then
(because it feels less threatened and less need to defend his territory),
and it will also permanently remove the chance of Testicular cancer for your
cat. If this is not possible because it is a pedigree show cat, keep it in
doors only. Not only will its coat improve in condition, but it is a lot
safer for it. Any non-desexed cat should be kept in doors at all times, and
all cats should be kept indoors at night. This is when they get into the
most trouble (beat up etc), and are most likely to do damage to wildlife who
just cant see as well as they do!
You could also try trapping it and getting it desexed by a local desexing
clinic. Some are very very cheap.
Unfortunately there isn't much else you can do, but like I said, if your cat
isn't desexed it should be indoors, anyways.
Good luck and keep us posted on what you decide.
Jade.