How to remove gaps in mesh during animation?

Ok, so i have this character which consist of 3 separate object-meshes: head, torso with arms, legs. Now, when i’m animating, it creates gaps in places where those meshes are connected and i have to admit i kinda expected that ^^ But is there any way to fix it / cheat it?

Btw, i need those to be separated coz i’m using them as items in game engine.

Make nearby vertices (of different objects) vertex groups as identical as possible.

Also make some overlapping - make head with neck a little further than just where armor starts