Hello Erskine Bevel,
Welcome to Microsoft Q&A forum.
An Xbox account cannot be linked to a Microsoft account, it will be created automatically when you use a Microsoft Account to sign in with Xbox services. Therefore, it cannot be moved from one account to another. Since you have your son used this account for Xbox before, the profile has been created since then. Before we proceed, may I know what you did when you said you have unlinked it?
I understand your concern about account security, so in this case, you can change your password first.
I'm waiting for your reply.