This thread is several years old but the rules are the same. For 2021 you can claim anyone if they lived with you all year and made less than $4,300 total income for the year. You can even claim your parents and Social Security doesn't count towarthe income limit.
See IRS Publication 501 starting on page 11 bottom Dependents
https://www.irs.gov/pub/irs-pdf/p501.pdf
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...
