Just helping my wife submitted two I-130 for sister/half-sister. The first case was easy and solid since it was the same mother and father. However, the second case is little bit complicated: mother is the same, but father is different. A side note: all the parents(all 3) are passed away long time ago. For the second case, beside the birth cert that showing the same mother, what's else do we need to submit to prove the relationship?