Head of Household is a special filing status used by IRS. Here is a link to the requirements to claim Head of Household.
https://ttlc.intuit.com/community/family/help/do-i-qualify-for-head-of-household/00/25539
You would need to answer yes to all 3 requirements to be able to use the Head of Household filing status. The article is written for 2020 but is true for 2021 as well.
Scroll down to the Related Information to see if your cousins meet the qualifying person that is required to allow you to claim Head of Household.
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