I reckon so. Wikip says: "Henry's death thrust Catherine into the political arena as mother of the frail fifteen-year-old King Francis II. When he died in 1560, she became regent on behalf of her ten-year-old son King Charles IX and was granted sweeping powers. After Charles died in 1574, Catherine played a key role in the reign of her third son, Henry III." Looks like three regencies, kind of.