Enroute Controller described a military in-flight emergency declaration that caused some uncertainty. The reporter suggested that more training be provided for these types of occurrences.

Narrative

Aircraft X; [in formation with aircraft Y and Z]; requested to break formation to continue into ZZZ IFR. While trying to input fight plans; aircraft X requested to stay as high as possible and wanted to try to proceed VFR. After trying to coordinate this; aircraft X declared an emergency for aircraft Z. Aircraft Y says; 'We are descending to 11;000 FT proceeding direct ZZZ.' [This was] totally unexpected. More training needs to be done regarding in-flight emergencies with military formations.