Do I really need to get my finches some chicks?

I started out with four male zebra finches. They paired off, of course, but a year ago one from each pair ped away. The remaining two soon paired off, and have been attempting to mate! I am sure they are not fighting, and am positive that yes, they are trying to mate. Nothing like this was going on before, and I can't find any information about cases of gay zebra finches. Is it natural? Should I do something?