All without kotr and has worked on the 1st try 5 times so far. I still have that game saved before killing ruby/emerald, so i might try again and see if i'm consistant enough.

Ruby: Only cloud alive, cast big guard to stay in haste, drink hero drinks during spare turns or attack, have 4x cut, at least 200 strength and speed, and use the w-item bug on elixirs/megalixirs/hero drinks. Only attack when you know there is a spare turn,(tentacles dead or an attack missed) and use omnislash only when fully healed, it'll take the tentacles out for the time being, while ruby takes a few turns to hit you and build your limit gauge up again, nail em, repeat. Long fight, but no need for chocobo breeding, and power sources are easy to find, morph the tanks in gongaga(sp?)

Emerald: Cloud, Cid, Yuffie, good speed and strength stats highly recommended, 200+ str on cloud is highly recommended. W-item bug on megalixirs, and make sure to use omnislash to kill the emeralds for a short time, so it can't use air tam storm.(dunno if i got that right, it's been around a year since i played ff7) Get both yuffie and cid with good strength/speed stats, and doom of the living and highwind will cause quite a bit of damage. No tact was involved with this strategy, i just got lucky all 5 times i suppose. No final attack+phoenix was used.

These bosses are like omega from FF5, just cheap, and once you find a way to kill em once, whatever method,(there are lots) you'll most likely find an easy way to kill them due to their easy to read attack patterns.