Transferring epic games account

unfortunately nothing can be transferred, and as the account is linked to epic that cannot be transferred either, it would have to be a new account and new epic account.

Yes, it will transfer if the Xbox account is connected to your epic games account

If you bought it with microsoft account and its linked to your epic games account it will be transferred

Hi,

sorry but can't transfer the games or progress to another account.

You mentioned the game Fortnite, I only know this:

if you access to your account from epic games, you can unlink the epic games account from the xbox account and then, that epic account can be linked to another microsoft account / email.

If the Xbox account is attached to an Epic Account (Fortnite game creator) then you may be able to unlink the current Xbox account and then relink it to your son's new account. I would check the Epic Games forums though to see if content would transfer.
You basically have to find out what Epic Account has all his Fortnite info. The previous user was correct that you cannot transfer achievements, or other game info. There may be a loophole with Fortnite and how it has a master Epic account that stores the
information.