Following are the rules to can claim someone (who is not your child) as a dependent:
1. The person must be a U.S. citizen, a U.S. national, U.S. resident, or a resident of Canada or Mexico
2. You can't claim someone who is claimed as a dependent on another tax return by someone else. Also, a dependent cannot claim another person as a dependent on their own tax form.
3. You can't claim someone who's married and files a joint tax return. ( This rule doesn't apply if the dependent files a joint return only to claim a refund of income tax withheld or any estimated tax paid).
4. They must live with you as a member of your household for the entire tax year.
5. They should make less than $4,700 in 2023 ($5,050 for 2024).
6. You must provide more than half of your relative's total support for the year.
If you satisfy all the above requirements, you can claim the person as your dependent. I have also included a link above, please go through that as well for additional clarification. If you like my response, please give me a thumbs up 🙂