Two Apple ID's and Family Share

Which Apple ID should purchase Apple One to share with the family?  There are two ID’s owned by the same person, me.  One associated with the older iTunes and the other unique to sync iCloud.

The original iTunes Apple ID has morphed into the Family sharing ID with purchases from others over time.  The second Apple ID was set up as a unique identifier for hardware and personal iCloud account syncing across various Apple devices.  Therefore personal devises are automatically logged into the unique second Apple ID. 

Currently my Apple devices are set up with the second unique identifier as the Apple ID and the older Apple ID listed for Subscriptions and Purchases.  

Does Apple and the App Store know it is the same person?  Or is my newer unique ID just another family member of the first that has to be shared with?  If the latter is the case, then I loose a family share number by having to share with myself.

I want to be clear that if the older Apple ID, that is set up for Subscriptions and Purchases, subscribes to Apple One, I will still be able to have 6 total family members use the Apps under Apple one.  Meaning myself and 5 other unique Apple ID’s.

At one point it seemed the older Family ID had to share with my newer unique ID so I could still have access to the original ID’s purchases and shared items.  This caused a loss of one share out of a total of 6 because I had to share back to myself.  In other words, if the Subscription and Purchasing ID stops sharing with my unique Apple ID, will I still be able to have access to and control over the legacy purchases and subscription because my Family Sharing account is set up listing the older one for purchases?   So the App Store, Music, etc. would know it is the same person and still be able to share with 5 others unique family Apple ID’s?

If I have to subscribe to Apple One from my unique ID to preserve the total of 6 shares, what happens to the connection to the older account?  Not that I like my kids music, but we sill want to be able to use what we bought.

Thank you,