How to copy the relations when duplicate a WI

With our usage of RTC we have a relation tree of work items where the parent WI always changes but the children sometimes changes.

One choice is to create a template of a whole relation structure, but this isn't good if at least one children won't change, then I want to reuse those WIs.

What I think I want is to duplicate my parent WI and the relations are inherited as the sam way as the "summary" and the "Filed against".