Hi ml, and happy New Year!
Welcome to Microsoft Q&A!
I understand you want to transfer your Minecraft and Xbox accounts from your Microsoft account to your son’s Microsoft account. Unfortunately, the short answer is that you can't (at least not as of currently).
Microsoft accounts are identity-based, and purchases are permanently linked to ensure account security and the integrity of digital licensing. Xbox and Minecraft entitlements are securely integrated with the Microsoft account used at the time of purchase. These licenses are associated with your individual Microsoft identity and are not designed to be transferred between different accounts.
In addition, game progress and achievements are tied to the Xbox profile, not the game license. If your son has been playing on your Microsoft account, those cannot be moved to his account. I'm sorry to share this unfortunate news, but I think it's better to be truthful and direct.
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