Lineage societies generally want one original document that names an ancestor’s parents to make a parent-child connection, such as the child’s birth certificate. Yet, not every ancestor has such a document. In that case, can you still join a lineage society?
Most societies allow the submission of what they call an analysis to make a parent-child connection. (In academic genealogy, it would be called a proof argument.) The standards are slightly different than they would be in academic genealogy. Societies typically want direct evidence of a relationship or documentation of a circumstance in which the parents you name are the only possible parents for that ancestor.
The most common types of analysis connect a child to their sibling and the sibling to the purported parents. In these cases, there is often a death certificate for the sibling naming their parents. While no such document exists for the ancestor, other documents may connect them to the sibling. They are perhaps named in an obituary. While evidence of a sibling relationship isn’t as strong as direct evidence of parentage, it does still make a connection – and many societies will accept it as such.
If you want to use an analysis in your application, be sure to review it with your society’s registrar or historian. Every society has its own standards. No guarantees about acceptance can be made in advance.