I am a US citizen and will petition for my sister and her family to immigrate to US. I know the requirements about I-130 and supporting documents from USCIS website. But I did not find anything about documents to prove my sister's relationship with her hu*****and and child.
Should I petition separately for each member in my sister's family?
What should I provide to prove my sister's relationship with her hu*****and and child?
Is it generally recommended to hire a lawyer for this kind of case and which lawyer do you recommend in southern California?
Thanks.