Start the greencard process though your brother. Use it as a backup plan.
The flight school will likely put you on a J1or F1 visa and after you have reached the ATP and officially finished your course of training you have to leave the country.
J1/F1 does not allow you to apply for a greencard as they are strictly student visas.
There is such a thing as an EB2 visa but you are not yet qualified for it.
https://www.aviationjobs.me/eb2-niw-...tm_medium=body
This means you’ll leave the US with 1500hrs and you’ll need to either do an EASA conversion or find a job with only FAA qualifications then apply for EB2 as soon as you qualify.
Alternatively look at flight training in Canada as their immigration policies are a lot friendlier.