Males will usually fight with each other. I've got 2 males and 6 females in my 50G and the males still chase each other around. I would keep 2 females to every male just to spread around the agression.
I've never had a problem mixing two swords together but thats JME. Depending on the individual (fish), and his personality you may or may not be able to keep two together like that. Its worked for me, but it might not work for you. Just a warning, for whatever its worth.