Parent & Child relationship can be a lot of different things, so for example on seller central you can have a parent and child account, for listing you can have a parent listing which has several child listings, listed under it, or even on Amazon shopper site, you can create a parent-child account, these things are simply that there is a parent which like the main account that have provided access to child users (secondary user), or in case of listing it carries the main listings under it.
