Oh dear, Re: the first dog eating his poo.
There are many reasons for this, the first is perhaps he was scolded for pooing in the house as a youngster and so learnt to dispose of the evidence.
The second is he is missing something in his diet, it has well been documented that pups and dogs will eat their own toilet if they have deficiencies in their diet, it is a natural instinct.
If this is the reason as already stated add pineapple to his food, this will give his faeces a none-palatable taste and will stop him from eating it.
Or feed him on a good dry food, not only will this fullfil his deficiencies it will also not be as appetizing as a solid mound.

The third reason is it may be a learnt behaviour if he were left alone for long periods as a pup and began eating this out of boredom, and thus it has become a habit.
The second brother I agree with JG begin to walk him sepertely for a while, when approaching a dog make him sit and bend down to his level, stroke him saying good boy if he is quiet and give him a treat, if he begins to snarl and bark say no and turn his back, it will take weeks of this for him to learn to be none-aggressive towards dogs and you will have to be very patient but in most cases especially with him only being 1 it should be trainable. But, if after trying this for a while and he still continues to be dog aggressive he must be kept on lead and perhaps even muzzled, he will need a proffessional behaviourist to help you to sort this out. Ask your vet for a referel if you can.