Littermates can bring huge problems and play-fighting can certainly escalate into more serious conflict as puppies mature, as Claire Arrowsmith explains...
(Q) I have a friend who bought two littermates. They are now five months of age and my friend is concerned that their play-fighting can get a bit out of hand. She was going to castrate them both at six months, but would she be better waiting to see how things go, or castrating only one?
(A) Behaviourist Claire Arrowsmith says: While castration is sensible in pet dogs, in this type of case it is often best to carefully observe the pups and to choose the lower-ranking dog to castrate first. This allows the gap between the puppies' characters to grow, leaving them less likely to compete over resources.
The problem with owning two littermates is that they are genetically similar and have had similar lifestyles, and so when they mature they both want similar access to resources. This becomes a problem when neither dog sees himself as being lower ranking or weaker than the other and so neither will back down without a fight. Castrating one and allowing the other one to mature before neutering him will help to avoid this scenario.
On a day-to-day basis, it is important to recognise that although each pup is equally cherished, the dogs themselves shouldn't be treated as complete equals. The relationship between the dogs will be healthier if their natural order is recognised and enforced during feeding, playing, and attention. This will make things clearer to the dogs and help to avoid problems while they mature through adolescence.
Play-fighting should be broken up before it becomes too rough, as this will help maintain more control over their behaviour and limit the potential for scrapping.