i130 - REF to establish parent child relationship - Sibling petition

[i130usa]

My sister filed i130 petition for me and now USCIS has sent us REF letter saying that we need to prove parent child relationship because my sister name is not added on her birth certificate and my birth was registered very late.

It also says that we need to a have at least one common parent. Now we have to submit secondary evidence to prove parent child relationship .I'm from India and the situation is that if my sister and I send our school/university mark sheet/ insurance, bank documents, all these document shows only father name not mother. And in the RFE letter it says that if secondary evidence only pertains to common father then we need to address the issue of ligitimation and provide marriage certificate which we don't have.

As we don’t have our parents marriage certificate I am thinking of going ahead and try to prove sibling relationship through mother. Only issue is there are only couple of documents that have mother name listed on them e.g ration card and passport.
I’m not sure whether these 2 documents along with affidavits will be sufficient to prove common mother relationship. Can someone please share their experience that might have been in similar situation?

[BombayParents]

Birth certificate for sister with blank name

Some municipalities like Chennai, do add the names later with proper documentation. They will ask for two or three independent proofs including SSC book, passport , ratio card, marriage certificate, aadhaar card etc showing date of birth, parents name etc.
In addition to the proof which should be countersigned by a gazette officer as true copy, an affidavit duly executed by your parents should be filed with a covering letter requesting the officer to include her name in the birth certificate. The whole process takes about two weeks if the paperwork is perfect. I have gone through this for my own case in Chennai and it was very smooth.

I don't have a solution for late registration.