If me 18 and my 17 yr old brother go to the airport does he have to have identification and if he doesn’t have a license or student if then what does he use??

Just to be clear, if they are just going to the airport (maybe to pick someone up...), then no ID is required. Otherwise, I would suggest you visit the TSA website and the airline to find out which forms of valid IDs are accepted.

Passport or birth certificate. Or state issued identificatiion...

It varies by carrier. You should contact the airline.