I am US citizen and would like to bring my sister and her husband with her twin 4 years old kids here, i would like the advice what is the fastest way to bring them here. For my understanding, i could : 1. Apply Green card for my mother who is my immediate relative and it will take about 1-2 years. And then my mother could apply for my sister, how long it will take? And will my sister be able to bring her family? 2. If i apply Green card directly for my sister, will she be able to bring her family? All my family are from Thailand, how long it will take for this way? 3. If i choose to apply for my mother, will she be able to go back and forth Thailand and USA while she is applying for my sister? Thank you for all replies.