The group clone creation has proved most successful for the ShinRa Underground as far as data goes. The groups display several matching traits and data, while also becoming tight-knit even after being released: something akin to twinship. Other JENOVAn qualities tend to match here, as well.
The fetuses in group tend to grow at exactly the same rate and grow the same body parts at the same time. The fetal group will often become active at the same time and sometimes appears to communicate with each other through, perhaps, some kind of psychic channeling. It has been theorised, and sometimes results show that talking to one fetus, giving encouragement and the like, will cause the others to mimic.
The tubal vat children tend to register each other and their surroundings better than single clones, and they will sometimes communicate with hand signals. Through growth, they often must be together or fits will be thrown. They will usually react the same way to everything, even if separated (so as to test a signalling theory). If in the playroom, they will often group together and play amongst themselves, some groups entirely losing their surroundings to their "siblings".
Through development, classes and lunches will be attended together, though breaks may be spent apart. They sometimes create their own language so the ShinRa Underground scientists cannot understand them.
As far as JENOVA goes, the changes are early on but they frequently match. The silver hair comes about in the same fashion, usually looking like highlights and receding backwards. Their eyes undertake a strange transformation at the same time, but they usually tend to happen overnight, or so most staff say. Their lefthandedness comes at about the same time, but some groups, together, choose to be righthanded or ambidextrous, so it is often up to the group at this point to decide, rather than when the single clone begins to become confused as his left hand begins to itch to write more.
As they are released, some clones will stay together, some separate. Interestingly, if ever a clone is to be recycled from a group, you can bet the rest of the group will follow. Tied close still, they would much rather go out together than "feel a void where my brethren is gone", or so one claimed.