
The standard answer to this is to reinforce the position of the dominant dog. Put his food bowl down first, greet him before the other one, give him his treat first (saying their names as you do it - this helps them learn each other's name, which can be very useful in the future). Maybe even let the top dog on the sofa but keep the other one on the floor.
In theory this should lessen their need for competition to determine status. They are in the early phase of their adolescence, when there are more hormones surging around than there will be when they are mature, so if you can get their pack order sorted out now there may be no need for castration. If after several months there is no improvement it is usually recommended to castrate the subordinate dog to reinforce the position of the dominant dog.
Generally once they have a settled place in the "pecking order" they are quite happy to stick with it.
Hope this helps. :)