One way would be to create an assembly, assemble the first component (the one you want the second component to follow), then create a Skeleton Model in the assembly, in the skeleton model create datum curves that follow the first part(using composite, intersection of surfaces using variable section swept surfaces...etc), create the second component in the assembly, create features using the the skeleton model curves, the draw back is that that second part is driven by the assembly skeleton but it does work well, I use this method alot.
i tried using your method but it seems that Pro/E do not allow that when assembly is using Insert command. otherwise, i do not understand how to create skeleton model. i hope that you would kindly provide more concise steps . Thanks a lot.