a US citizen can petition for their stepparent to immigrate to the United States, but certain conditions must be met, including the stepparent's marriage to the US citizen's biological parent occurring before the US citizen turned 18. So this is something you need to resolve first.
They adopted, but not legally ..... if not legally adopted then something else you need to resolve first as neither you nor your father can sponsor someone who is not some sort of legal relative.
Your sister is an F4 candidate. Current times for US citizens to sponsor siblings is around 15 years.
For Permanent residents (your father) to sponsor adult non married children (21 years+) 10 years.

This post should be moved to the US general section ....

 

Thank you very much, Crawford! I think an moved my post (sorry about that!)

I will check with my father when they got married.

As to my step brother, we can do the Hague Convention process right? But is it gonna be more costly and complicated if we do that compared to doing the legal process of having my father adopting my stepbrother domestically in the Philippines and petition my father with him since he is a minor? Thank you!

 

Where do the Philippines come into play please?

 

Hi, Crawford. So I just found out that they got married when I was 18yrs old and 9 mos. Legal age in PH starts at 18. I suppose my dad can only petition them once he becomes a citizen? I will google it. If you have any advise on what to do, please tell me.

Thank you!

 

I suppose my dad can only petition them once he becomes a citizen? I will google it. If you have any advise on what to do, please tell me.

Thank you!

Your father can petition once he becomes a US permanent citizen (green card holder)

 

What's the Hague convention pertaining to your situation?