In the Pathfinder setting, hags and worshipers of Gyronna sometimes replace babies with changelings. I'm considering an adventure in which the PCs defeat a Gyronnan cult and find a kidnapped baby in their lair. This raises the question of how the PCs can find the family of a pre-verbal infant.
One solution I've considered is the spell Blood Biography. However, looking over the text of the spell, I'm not sure it would work (important parts highlighted):
You learn the answers to a specific set of questions about a creature so long as you have access to at least one drop of its blood. You can cast this spell on the blood of the living or the dead, but living or undead creatures are entitled to a Saving Throw to resist the spell. You can cast the spell on dried or fresh blood. Once you cast the spell the answers to the following four questions appear on any flat surface you designate (a wall, a piece of paper, and so on).
- Who are you? (The name by which the creature is most commonly known)
- What are you? (Gender, race, profession/role)
- How was your blood shed? (Brief outline of the events that caused its wound, to the best of the victim’s knowledge)
- When was your blood shed?
These answers always appear in a language you can read even if the creature cannot speak that or any language.
Clearly, the answer to the question "How was your blood shed?" depends on the target's knowledge. However, the same text isn't present for any of the other questions. So the question is, does the baby have to know its own name in order to answer "Who are you?"
The phrasing "The name by which the creature is most commonly known" makes me think that it doesn't matter if the baby knows her own name. However, I'm not sure because spells like Speak with Dead definitely do depend on the target's knowledge.