OCI Card

Me and my husband have both applied for OCi Visa. My husbands parents are both deceased so we thought it would be easy, as we had their last passports which shows their place of birth and we provided their death certificates. Only my mother was born in India and she is still alive. I provided her indian passport also provided the surrender certificate for this passport as she now has british citizenship. We sent off the application with the relevant fee and all the necessary documents with copies. But everything was returned. We are now being asked for my husbands parents proof of birth in India, also even though I provided various documents with my mums name on it appears that my birth certificate notes my mums maiden name and not her married name and they want an affidavit to confirm that she is who she is on my birth certificate. That is not a problem I can attend to this. But what astonishes us is that they want my husbands parents proof of birth in india. They were born way back in the 1915 and 1921. We do not have any documents to prove their birth. Can we get copies of birth certificates from India, I know this is a long shot but we just do not know what else to do. Can someone help us please with a way forward. They are also asking for a letter from my husbands work place, but not mine. We have both been in the UK for a long time and working for a long time so why do they want this from him but not from me.