Direct evidence speaks to the point in question. Indirect evidence gives facts from which you can come to a conclusion.
[Evidence and Documentation]
Funeral and memorial cards may supply information that obituaries do not.
Can’t find any male relatives who inherited your maternal grandfather’s Y-DNA? Cast your net wider by climbing further up your family tree. See if that grandfather had brothers who had sons, or if his father (your great-grandfather) had brothers who had sons.