Birth certificates
Order certified copies from the state vital records office (or county in some states)
Some steps differ by region inside the country.
Where
The vital records office of the state or county where the birth was registered.
How
Check their own files first, the original is often already there with the will.
Order from the vital records office of the birth state, not the state where they died.
Order the long form version if it is needed to prove parentage or citizenship.
Use the CDC directory to find the correct office and its current requirements.
What to bring
Their full name at birth, date and place of birth
Their parents' names, including the mother's maiden name
Proof of your relationship or your authority
Payment for each copy
Timing
Mail orders commonly take 2 to 8 weeks depending on the state.
Sources
This is practical information, not legal, medical, or financial advice.