I should probably being by describing a bit about my cats to give as much info as possible.
My oldest of the three is a girl, Peaches. She is a huge suck, to the degree that if you ignore her, she will make sure you give her attention by standing in your view or just standing on you. I call her Princess Peach as a nickname. She is fixed and declawed.
The middle kitty is named Stubs, or Stubby(due to his rabbit like stub for a tail), and he is stubborn as he doesn't come when you call(the others do), and he is very much a 1-on-1 cat and prefers to be with someone when they are alone. He is also fixed and declawed.
The last cat is called Baby, as he is a huge suck. He loves nothing more then attention and even knows how to do the "Hello" meow which I always found comical. He is about three so he isn't named Baby because of his age, and lack of a creative name.

He isn't fixed, or declawed though.
The other night Baby, and Stubby got into a huge fight like never before. I've never heard Stubs yelp so loudly, and we tried to stop it as quickly as we could. Stubby got a good mark by the bridge of his nose, right by his eye and we were very glad we stopped it before it could go any further.
We assume it is territorial aggression, and now Stubby won't even let Peaches near him. Not attacking her mind you, but he will growl, and hiss. She usually just backs off. So I think Stubby is more of the defender in this case. Then again I'm no animal expert so I don't know for sure yet.
She has been able to approach him a few times when he calmed down, but if it is within 25 minutes as least within seeing Baby he also shows hostility towards her. She did at one point walk right up to him, and sniff him in the last few hours and he payed her no mind. The issue is if Stubby does keep up the aggression towards her, do we give him up? It's honestly the last thing we want.
Baby is the one I've always seen charging, as even with Peaches, Stubby's reaction is just sit back, get defensive and hiss and growl. The thing is we also love Baby to death, and we don't want to get rid of him either, but he seems to be the aggressor.
The issues I have is will Stubby be the same with him, or more so if he do HAVE to get rid of Baby will he show the anger towards Peaches still. It is the last thing I would want honestly, and I couldn't forgive myself if I gave Baby away for Stubby to never be the same again.
Then again, I don't want Baby charging at him, and he doesn't do anything to Peaches, he doesn't even care and only focus' on Stubby which is what makes me feel it's territorial. I just haven't seen them go at it like this before, and my family is all worried about them. We don't have the money for a vet trip to concretely figure out what's going on. Our assumptions are our best thing we can do at the moment, but the last thing we want is to make the wrong choice.
Both are still showing signs of hostility on the second day, and Baby even charged him again earlier which I quickly broke up(not without scratches though). After this Peaches got nosy again and Stubby won't let him near her...again.
So any tips, or should I just wait it out and see. The possibility of one going within the new few days seems like a very real chance though. All three of them got along very, very well beforehand none of them are actually family, but they always acted like it.