Proof of sibling without birth certificate

[ssdesign]

Hi,
I am a US citizen and want to apply for my siblings I-130 but I do not have a birth certificate.
What options do we have to prove that my sibling is my biological brother in the absence of birth certificate of one sibling?

Any help is appreciated.

Thanks

[newacct]

Why do you not have a birth certificate? The visa reciprocity and civil documents by country page for your country of birth may list alternative documents that are acceptable in lieu of a birth certificate.