1. spell out the adoption relationship provide the adoption court records , 2 years of physical and legal custody proof at time of I-130 filing .
2. Document the family blood relationship ( child of your sibling ) birth cert and death cert for your sibling
3. Absolutely address the issue of child habitual residency ..
4. Ask USCIS to review the response to RFE and issue any clarification on further evidence if required, reaffirm the DNA testing will not establish a parental relationship and was issued in Service Error
https://www.uscis.gov/adoption/immigration-through-adoption/family-based-petition-process#Children from Hague Adoption Convention Countries
Thanks for share! I thought about the RFE may have been issue in error but couldn't considering all the form I-130, birth certificate, adoption and custody were provided, I couldn't imagine it was an error. I have planned to do the DNA and issue additional letter. Thanks for your input!