First of all you can only claim him as a dependent if he had less than $4,400 total income for 2022. He would have to say he is a dependent on his return and can't claim any dependents of his own. If he's married he is probably filing a Joint return with his spouse.
You need to claim a qualifying dependent to get Head of Household. Here's a FAQ for Head of Household
https://ttlc.intuit.com/community/family/help/do-i-qualify-for-head-of-household/00/25539
Who is a qualifying person for Head of Household
https://ttlc.intuit.com/community/family/help/what-is-a-qualifying-person-for-head-of-household/00/2...
