The Parent LLC should be set up as the “Holding” LLC. The Holding LLC will own all the Shares in the Subordinate LLCs.
Sub A LLC though Sub Z LLC will give Holding LLC a K-1 each year. The SUB LLC will not need to file a tax return as they are disregarded entities. However, your CPA will need to do the books to produce the K-1’s etc.
The financials work exactly the same as if you owned the Sub LLC’s directly, with the exception of not needing to file a tax return for each Sub LLC.
Since you and your Partner’s own the Holding LLC you will only get One K-1 from the Holding company. Instead of 1 through X LLC K-1’s.