I have the interview for citizenship early march (so hopefully April will be the ceremony), my brother is here in the states and he's Tourist passport issue visa b1/b2 expires on march too, but he permission to stay here on the usa was given until may, should we wait until April when I become a citizen (so I can request him then) or should we do it before he's b1/b2 visa expires on march (as a resident) thanks

To petition brother/sister takes about 10-12 years. He must return to his home country immediately... don't overstay.
It will make things easier and you don't have to pay expensive attorney fees.

lawanwadee is correct.

After you get US citizenship, you can start the process for your brother. But after you file the I-130, he cannot file for permanent residence until a visa is available in the 4th preference category, about 10 years. At that time, he can get permission to stay, if he is here lawfully.