[luckypenny]

If I understand the post, these two dogs share the same home and have gotten along great for the past two years. Also get along great with other dogs. One is 3 and the other is 10.

Other than "playing," there aren't enough details to determine how the first altercation started. The second one was while food was being prepared. These 'fights' are sudden and recent.

Dogs have a way of communicating with each other using subtle body language and facial expressions...something that is often difficult for the untrained eye (meaning us humans) to pick up on. If one dog does not understand and/or doesn't respect and/or can't see or hear what's being communicated, often trouble can result.

Is the younger female the more dominant of the two? My sense is that your older dog may not be reading the body language your younger one is displaying. Perhaps he came too close to the her bowl? To your father while he was preparing their meals? Without seeing exactly what happened, it's hard to determine what's going on between the two.

One thing I do strongly suggest, is that you have your senior dog's vision and hearing checked. This may aid in determining whether or not he can read your other dog's cues and whether this may be contributing to the sudden problems between the two.

Until you find some concrete answers, please feed both dogs separately and provide constant supervision when they are together.