Always identify the handwriting on old photographs, especially if multiple individuals have written on the back of the photograph. Tracking this information helps to evaluate the probable knowledge of the informant and preserves it for others who may later see your image of the photograph. It may also help someone else who has pictures from the same family that may have writing on the back.
I realize not every one has photos that are identified. Not all of mine are, but when I do have ones with writing on the back, analyzing that information as best I can is important.