To share an instance of the class indicates that they are not children of that class but that there are several different objects being used.

[pascal]
TextureManager := TTextureManager.Create;
LightingManager := TLightingManager.Create;

FileSystem := TFileSystem.Create;
TextureManager.FileSystem := FileSystem;
LightingManager.FileSystem := FileSystem;
[/pascal]

This means that a FileSystem is created and each of the other objects can use the information available in that FileSystem Object.