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Canines (dogs) and cats kill their prey by asphyxiation, literally choking them using their teeth and jaw to cut off the ability to breath. It is also used by cats and especially dogs to determine rank in the pack. If your dogs are biting one anothers necks or throat they are trying, aggresively, to establish rank or position in the pack.
You are, more than likely, regarded as the pack leader, the big boss, the other two dogs are attempting to establish who is dominant under you and this is what they are doing.
You didn't mention if the dogs were mixed gender, male and female, if that is the case the female may be warding/fighting the male off and the male may be attempting to initiate 'reproduction'. This is unlikely and most probably they are trying to establish dominance amongst themselves in the 'family pack'.
To avoid it or reduce it you could try feeding them seperately, keep at least 3 meters between food bowls and make sure they hae seperate water bowls too. Find time to groom both dogs but do it when they are apart so that no jealousy develops. Dogs can be very terrortorial so you have to take that into consideration as well as the fact that they can have huge amounts of loyalty to their 'owner' and will become aggressive towards anything that they perceive as a danger ot threat to their owner - that can include petting another dog even if it is a dog they grew up with.
Never forget a dog is a barely tamed animal, cute, family friendly it may be but it can turn. Scariest animal episode I ever had was when a poodle turned on me, one minute cute ball of fluff, next minute fangs bared going for my throat - scared the **** out of me.