Display each submenu separate

I have a problem. In the layout I’m working on I have three menus, the first one is for parent, second one is for child and third is for grandchild. Each menu is separate from the other. So far, what I’ve done is create a whole bunch of menus (one for each child menu and one for each grandchild menu) with different names and display them in different templates, but this is less than ideal.

Let’s say I have 5 parent pages, which each have 5 or so child pages, which in turn each have a bunch of child pages (grandchildren). Now, if I want to display just the parent page menu + one child menu related to the current parent page. In the next one I would like to display the parent page menu + current child menu + current child grandchild menu. How would I go about doing this? (other than creating a bunch of separate menus)