Reporting Services :: Group And Sum Items / Sub-items Into One Record

I'm having an issue creating a report that can group & sum similar items together (I know in some ways, the requirement doesn't make sense, but it's what the client wants).

I have a table of items (i.e. products).  In some cases, items can be components of another item (called "Kits").  In this scenario, we consider the kit itself, the "parent item" and the components within the kit are called "child items".  In our Items table, we have a field called "Parent_Item_Id".  Records for Child Items contain the Item Id of the parent.  So a sample of my database would be the following:

ItemId | Parent_Item_Id | Name | QuantityAvailable
----------------------------------------
1 | NULL | Kit A | 10
2 | 1 | Item 1 | 2
3 | 1 | Item 2 | 3
4 | NULL | Kit B | 4
5 | 4 | Item 3 | 21
6 | NULL | Item 4 | 100

Item's 2 & 3 are child items of "Kit A", Item 5 is a child item of "Kit B" and Item 6 is just a stand alone item.

So, in my report, the client wants to see the SUM of both the kit & its components in a single line, grouped by the parent item.  So an example of the report would be the following:

Name | Available Qty
--------------------------
Kit A | 15
Kit B | 25
Item 4 | 100

How I can setup my report to group properly?