PaulH0 is wrong. You can claim anyone any age who lives with you that’s has less than $5,050 income. Some Dependents don’t even have to live with you.
See IRS Publication 501 there is a table and rules starting on page 11 and page 19 Gross Income Test.
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...
