Primary and alias emails to try and separate x box and Microsoft accounts?

nope, even with a new alias he will still use the same password as you and still get your emails, there is no way to separate the accounts.

you used to be able to change the account associated but everything was merged years ago, its because the xbox account is the microsoft account, they are one in the same, same goes for skype, teams, office etc etc.

my kids have had there own child accounts since they were young and when they turned 18 they changed to adult accounts automatically, and now they manage their own accounts and not lost anything.

Maybe I wasn't clear in what I was hoping to accomplish or perhaps I'm misreading your reply. You said he could create a "new Xbox account" but that would mean he loses everything he has under the current one, wouldn't he? Ideally we'd love to have him have a separate account entirley but either I lose my office services or he loses his xbox stuff.

I guess what I'm trying to ask is if I can have my email and his alias email on the same account but assign his alias to his xbox stuff? Under that scenario he keeps all of his xbox account stuff but accesses it with his own email. I hope that makes sense.

I use gmail for my emails so that's not really a concern. The only thing I use Microsoft for really is Office 365 on my home laptop - I have a work Microsoft account but use my work email for that. I'm phasing out the email that's currently associated with my Microsoft account (a cox.net address) and was trying to find a way to keep everything but try to give him some anonymity with his xbox.

I'm probably just going to not renew my office 365 on my current email, repurchase on my new email and sign over the Microsoft account to him. Just seems silly there's not a way to transfer xbox data to a new email address.

You can add the account without losing the data.