I am a US citizen and was looking into my father to be immigrated to US. As I read, I-130 (Petition for Alien Relative) needs to be filed. And I would need to prove the relationship. The I-130 instruction says that I would need my birth certificate showing my parents (father) name and my father's marriage certifcate showing that he was married to my mother (deceased now) before I was born.

My questions are:
1. What if both of the above documents are not available? Are there any alternate documents?
2. Are these 2 the only documents needed and thats it? (I had recently filed I-129F for my fiancee and the paperwork needed there is way too much; in comparision I-130 requriements for relative are minimal, so want to double check)