I have had a lot of issues with dogs fighting in the same family for awhile now. They may be getting along great for years and then all of a sudden they get into a big fight. There are always certain triggers that can set dogs off such as food or favorite toys. My own dogs tend to fight for attention at times. It can be very scary and if it is happening a lot please seek professional help. If it is not a serious fight and they seem to get along most of the time I think looking for the triggers that seem to get them stressed out is very important and try to avoid these behaviors. If they fight over food just separate them during meal time. If they are very territorial about a certain toy maybe keep that toy away from the other dog in a safe spot. It is always really stressful when dogs get into a fight but a little bickering is quite normal. If you are concerned about the fights there are many great trainers in out area that can help out.