Hi 8 Laoshi,
Sorry, I am typing in English. My case is like this.
I am a U.S. citizen, and my parents got green cards from me for 3 years now, and they do not have any income. My sister is 40 years and single. If we want to petition for my sister to live in the US, do we have to petition via me or my parents can do that for her?
Thanks so much!