Hello, Your parents' cases are straightforward. You must file one I-130 for EACH of them. You should also file an I-130 for your brother, but because sibling applications take a long time, your parents will also need to submit I-130 for your brother after their green card is approved by the US Embassy. Your parents should be able to receive the green card within 8 to 10 months. However, your petition for your brother can take 8 to 10 years to become current.
After your parents enter the US, they should submit a new I-130 for your brother as new permanent residents. Their petition will be pending for about 2 to 3 years. If your brother is still under 21 when the visa number becomes current (currently projecting about 2 years for child of permanent resident [your parents]), then he will get a green card before he turns 21. If he turns 21 and the visa number is not yet current (possible, depending on how quickly your parents get their green card), then he will have a longer waiting time, roughly 5 to 6 years, before he can get the green card to come to the US.
As you can see, your brother's case is the unpredictable one. I recommend filing for your parents as soon as possible so that they can turn around and file for your brother for faster processing.
Answered on Jan 17th, 2011 at 10:58 AM