4 U.S. citizens or permanent residents (must over 18 years of age, and have enough financial support) can handle Family-based immigration for their parents.
5 strongly recommended: Cancel "F4 kind of immigration" soon.(for American citizens' brother and sister)
6 About F2B & F3 kinds of family-based immigration(for U.S. citizen or permanent resident's adult children, over 18 years of age.):
Since the near future: (strongly recommended!)
Strongly recommend to cancel F2B & F3 kinds of family-based immigration soon. (for U.S. citizen or permanent resident's adult children, over 18 years of age.)