Hey!
I’m sure there has been many posts on this specific topic but I was not able to find the help I need on this case.
I’m still pretty new to blender and currently working on human character made of multiple meshes.
so joining the meshes in to one is not an option.
When rigging the character and then moving the bones the seams of the different parts doesn’t follow nicely.
I’m open to different suggestions, and thanks in advance 
Well, the ultimate answer is that if you want the “seams” to move together-- ie, it’s an organic figure, not a robot-- then you make it a single mesh.
If you’re not ready to do that yet, then verts with the same weight and the same starting position will deform into the same deformed positions. So make sure that your “seam” verts are in the same location as each other, with the exact same weights.
Hi, is there a reason to why you don’t want to join the body parts?
The top and bottom mesh looks exactly the same.
hey! thanks for the answers
bandages, I was able to do it for that specific case but for some reason the same trick does not seem to work for joining torso and upper arm…
and for digitvisions, I was thinking on making a game with modular character parts, so you could switch the head, torso etc. with another mesh. Reading lots of forums, it seems that modular character parts might be the way to go, ofcourse again, im open to suggestions 
if you need to sometimes change the topology so that it bends the way you want you can try shapekeys, not sure you can export that in games though…
I am not familiar with modular character parts but if you are weighting the parts to the bones like bandages suggested you won’t be able to detach them again without messing up the mesh.
And if you parent them to bone as object they will not be as one piece.
That would be weird. If you link a file, I’d investigate myself.
Note that with modular characters, you’re still going to want to be separating objects at more natural divisions. You’re unlikely to want to separate at the elbow, for example, because a sleeve is a single piece.
thanks for the answers! I’ll look into the things you guys suggested!
and for the file, I get error that I cant upload files since im a new user
They don’t have identical weights. The seam on your torso is equally weighted (1.0 to both) to both chest and arm. The seam on the arm is weighted only to the arm. When I remove the chest weights from the chest seam, they match.
You sir, are genius! thanks a lot!
In case anyone finds this thread while looking for a solution to a “shading seam” that appears along an edge loop when you modularize/separate a moderate to high poly mesh up into several body parts e.g. separate a body into a head and a torso, as I have just done, the solution to the shading seam is to join the parts back together again, merge vertices by distance to remove those vertices with the different normals, split the edge loop where the seam is e.g. around the neck when splitting a body mesh into a torso and a head mesh, then separate the body parts up again into several objects. Explanation: The splitting of the edge loop where the seam is , creates 2 identical edge loops with identical normals. When subsequently separating the mesh into several objects (body parts) those normals are retained (stay the same) and thus the shading along that edge loop is retained.
