Rotating scene or complex object using center of AABB
Solution:

Instead of re-calculating center, pre-defined center is used for primitives. The pre-defined center is center of AABB if other value is not supplied. Averaging all center of mesh primitives gives mesh center and averaging all center of meshes gives scene center. After a mesh is transformed, center also gets transformed. 

Now center is not moving after rotations. Using center of scene's AABB seems not good idea. Because each shape of child AABB is changing after transformations.