[quote=Otaku95]
So, in a nutshell, the only way the brothers could learn to control their beast forms would be to find something that's worth protecting, be it a brother or lover.
[/quote]

I like this idea, so how about this: 

The brothers have very little control over their beast forms for now, save for the rare occasional moment of clarity. I'll let you decide when that happens. 
Once they get closer to someone and start to form a strong bond with them, telepathic possibilities may start to open. It probably would work best when there is a mutual feeling there, so I might set up a specific requirement before there can be full telepathic communication. It won't be anything too big, but I want it to be meaningful. 
If someone they care a lot for steps in, the beasts may gain a sense of clarity and will be able to better control their forms. 

As for the controlling bit... Hmm... it sounds a bit awkward like that, but perhaps the girls have a bit more influence over them when they are in their beast forms? Also, when they master their telepathic abilities, I don't think that there will be quite so much "controlling" as reasoning. I believe in two-way relationship streets wherever possible. Call it what you like. 

So, to recap: Beast forms require a Beauty's involvement for control, except on certain occasions. I'll let you decide if you want the relationship between brothers to have influence on that as well. Personally, I think we could have some nice heartwarming moments with something like that. 

Hmm... what about telepathic abilities between brothers...? Thoughts?