1. To be doubtful is to be uncertain of an outcome. It is to question whether something is real or true. A doubtful character would be known to question things and would often be uneasy.
2. “Mexicans are always making things up. Grandma Jefa told us the week before she died. Don’t ever believe these family legends people have. It’s like how white people like to say their great-grandmother was a Cherokee princess, but worse.” (“Everyone’s Abuelo Can’t Have Ridden with Pancho Villa”)