A death record or cemetery record is good proof (at or near the time of the event) of DEATH but it is NOT proof of birth. The person giving the information on a death or cemetery record may not have any valid reason to know the date and/or place of birth.
Do you know where and when the birth occurred? Do you know whether the state HAS birth records available for the year of birth? Pennsylvania for instance has birth records at the state level (fairly reliable) beginning 1906.
You mentioned church records...WHAT church record? If you have a baptismal record recorded at or near the time of birth (usually prior to age 5) this can serve as a good proof of birth IF a birth certificate is NOT available...and you have a written statement that this is the case from the state.