Question: Who is the mother-in-law of Johannetta Of Sayn-Wittgenstein (1632–1701)?
Sentence (from "John George I, Duke of Saxe-Eisenach"): His fifth and only surviving son, Wilhelm August, was born eight days after his father's death and became duke from the moment of his birth; Johann George became the regent of the duchy and also the guardian of the new duke.
Relevant evidence: No