Hi.
Neutering just one won't fix the problem.
They are 6 months now so they will become hormonal inevitably and both, just the first one started earlier, but they will both be hormonal and will be humping each other and spraying urine all over and peeing and leaving stinky wet poos everywhere to mark their territory.
In fact, when you've got them they were not bonded, they were just babies and it always changes when they enter their hormonal phase, they start humping/circling, then fighting and it can (and will if you keep them together) end up in blood. Boys would usually become hormonal at 3,5-4 months but sometimes later like 6 months is a bit late I would say, but it is individual.
In your situation I would immediately separate them so they can't even see or smell each other (that's important), and I would spray my hands and clothes with 5% vinegar if I will hold them so they could not smell another rabbit, they can start showing aggression towards you and even bite. This is best to prevent than cure.
If you want to keep them together, both must be neutered and you will have to wait at least 2 months after that and keep them completely separately before you can start bonding them.
If you will separate them as I said so they are unable to smell or see another rabbit they will calm down a bit but you cannot stop that process of becoming hormonal, it's just nature.
One way to stop it is neutering (boys still stay hormonal about 6-8 weeks after neutering or sometimes even longer, they still fertile for a few weeks after neutering too, that's why you will need to keep them separately) or just keep one rabbit and let him or her overgrow their hormonal age naturally (it may work, but depends on their personalities largely), it can be after 1 year or two years for larger breeds. But when you have another rabbit there they are both under stress and if they are both boys there's competition so they will show hormonal signs more than if they see no other rabbit.
From what you described that one of them became territorial and attacks your hand, can you give more details about being territorial, is there also humping/circling or grooming just describe what you see.
In my experience I have raised many rabbits myself and I am a pet behaviourist specializing in home pet rabbits, it is more common for females to show territorial signs as you described. I would re-check their gender right now are you sure they are both boys?
Here's how you can do it yourself
https://www.rabbitsonline.net/threads/sexing-rabbit-pictures.44936/