Applied I-130 for parents. USCIS is asking for "REQUEST FOR EVIDENCE" to proof my relationship with my parents. Anyone had the same issue and provided the Affidavits from 2 different people with a statement affirming the relationship. If yes I would be thankful if anyone has a sample of the document.

I went to the wikihow site and created a sample. Probably it will be something similar. Since you already know that affidavit is merely a written statement confirmed by oath or affirmation, for use as evidence.

The attached is only intended as a sample. You may refer to your immigration attorney for more details.
This is just to provide an example, that preparing an Affidavit could be a simple process.

Probably one can create one affidavit each for each of their parent or relative.

Source:
http://www.wikihow.com/Write-an-Affidavit

Thank you...

Didn't you submit your birth certificate to the USCIS when you applied I-130 for your parents? if not, ask your parents to make your birth certificate that includes both your parents name and your name with your birth location. If your birth certificate is in Nepali language, do not forget to translate in English and also certify it with authorized personal in Nepal and submit both to USCIS. Other than that you really do not need any affidavit from other people. You only need affidavit, if you do not have your birth certificate and you can not make it in Nepal.

Besides this, another thing I want to suggest is, anytime you have any issue with USCIS, you can always contact your local congressman. You can find the name of your congressman by googling the zipcode. They will have a USCIS liason in their office, whose task is to talk to people in USCIS directly.

In my case, I forwarded such type of proof of evidence to my congressman's office, and the liason forwarded that to USCIS. The case was decided much more quicker through this route. I highly advise you to take this route.