Leopold VI, Duke of Austria is the father-in-law of which person?
CREATE TABLE "queens_of_bohemia" (
  "father" text,
  "birth" text,
  "marriage" text,
  "became_queen" text,
  "ceased_to_be_queen" text,
  "death" text,
  "spouse" text
);
SELECT "spouse" FROM "queens_of_bohemia" WHERE "father"='leopold vi, duke of austria';