You can not file as Head of Household. Need to have a qualifying child. But you can clubman him as a dependent.
Who can I claim as a dependent?
https://ttlc.intuit.com/community/credits-and-deductions/help/who-can-i-claim-as-my-dependent/00/267...
He might have to file a return as a dependent. You don't have to file if you only have W2 income under 14,600 but you can file to get back any withholding taken out in boxes 2 or 17. But you don't get boxes 4 or 6 back. If you got a 1099Misc or 1099NEC you have to file it as self employment income no matter how small the amount.
Filing requirements for a dependent
https://ttlc.intuit.com/community/children-dependents/help/do-i-need-to-file-my-own-taxes-if-i-m-a-d...
