I have a US citizen sister, my father's daughter. However, we do not share a last name and there is no indication on any offical records that she is my father's daughter. My father has already passed away, but we (my sister and I) have a close relationship.
I'm interested in knowing if there is any possibility for me to acquire a green card through her sponsorship. Can I "prove" that she is my sister through DNA testing or somehow else get a green card based on our close family relationship?