Complex sentence: In 1703 the Marquisate of Douglas was elevated to a Dukedom, however, in the late 17th century, more political power was wielded by the Douglases of Drumlanrig, in Dumfriesshire who are also descended from the Black Douglases.
Split into simpler sentences: In 1703 the Marquisate of Douglas was elevated to a Dukedom. By the late 17th century, more political power was wielded by the Douglases of Drumlanrig, in Dumfriesshire who are also descended from the Black Douglases.