Complex sentence: Although family relationships sometimes became problematic, Wu Zetian was the mother of three sons who served stints as emperors, and one of her grandsons became the famous emperor Xuanzong of the restored Tang dynasty, ruling during its "Golden Age".
Split into simpler sentences: Although family relationships sometimes became problematic, Wu Zetian was the mother of three sons who served stints as emperor. One of her grandsons became the famous emperor Xuanzong of the restored Tang dynasty, ruling during its "Golden Age".