It's not just two males...I have 1 male and two females, in age from 2 yrs old, 1 yr old and 9 mos old. The two girls will fight for attention. They want the attention from the male. They will fight over who gets to be closest to mom. When the older girl went into heat a month ago, I thought I was never going to get to sleep for 3 weeks. When I am home, I can keep an eye of them. Now I have learned (the hard way) that when I have to go somewhere for over 30 minutes, I must crate at least one of the girls.
I also have learned that one Doberman is a piece of cake. Two Dobermans are a bit more of a challenge. Three Dobermans become a pack, and that becomes PACK MENTALITY!!! Even in play, two will gang up on one, and it can turn ugly really quick. Their games never start out as a fight, but it can turn into one really quickly. I am never more than a few feet away, I carry a spray bottle of water all the time. I have my hose turned on JUST IN CASE (spray nozzle at the ready). Even a simple thing like one jumping into the bed to go to sleep can turn bad if the girl happens to land in a "bad spot" on the boy!!!! He is very protective of his family jewels!!!
I go to sleep with the spray bottle on my night stand. Some nights just one pup trying to get closer to me can lead into a confrontation. I love my pups, but I also know that they are dogs, and natural instincts are stronger than all the training in the world. Especially when there is more than one Dobie in the house. I have no fear of my dogs for my own self, but I do fear for them if left to their own devices.
Dobermans are one people dogs, and as such, they have a hard time sharing that person with anyone or anything else. Especially one of their own. It was easier for me to have one of my cats near or on me when I had one Dobie than it is to have one Doberman closer to me when I have 3 of them.
I now have to keep my poor cats confined to three rooms in the other side of the house. If I allow one dog at a time around the cats, NO PROBLEM. But the minute all three see one of the cats, that PACK MENTALITY kicks in, and it is corner the cat time. I will not allow that, so for my cats' sakes, I keep them separated. One of my Dobie's was not raised with cats, and she is the one that will start the "get the cat" and the other 2 (even though they were raised with and get along with the cats) will jump in and go nuts to get the cat. Ironically it is my smallest cat that causes the problem. The older, bigger cats will run and hide from the dogs, but she is fierce and will stand her ground. NOT a smart move around 3 Dobies.
And this is how you learn to live your life when you are owned by cats and Dobermans. No one said it would be easy, and it isn't, but it does have its rewards.
I hope that having your boy fixed will help, but if he has already learned to mark territory, it might be worth your while to look into getting a crate or two. I never believed in crating any animal, but when it comes to their own safety, I learned that this is better than the alternative.
Good luck!!!!