Question: Who is Marcus Aemilius Lepidus (Executed 39)'s maternal grandfather?
Sentence (from "Marcus Aemilius Lepidus (executed 39)"): He and his sister Aemilia Lepida were both married to siblings of the Emperor Caligula (Aemilia married Caligula's elder brother Drusus Caesar; Lepidus married to Caligula's younger sister Julia Drusilla).
Relevant evidence: No