Render two objects as one.

Hi everyone, I’ve started to “play” with Unity recently, and I’m stuck right now.
I have two objects as child and one empty parent object. I want them to appear as one object.

As you can see in the screenshot, in case of cubes everything is fine. But in case of cylinder and the capsule I have a line or an “overlapped?” area.
My final objective is to move these child objects (separately) but render them as one object (like the cubes). Can you give me any solutions for this?

Thanks in advance

I’ve tried Combining the meshes into one but… By the way: after “mesh.CombineMeshes” operation do I have to remove duplicate or overlapped geometry or the Combine removes duplicated (and/or hidden) geometry?

Use 3d modeling program to create composite mesh. Runtime composition is very advanced topic: Boolean operations on polygons - Wikipedia