
Yes, when he married Anne Scott, 4th Countess of Buchleuch, he took not only her title (which got upgraded to Duchess of Buchleuch), but her surname. He would have been James Fitzoy previous.
Quote:
On April 20, Monmouth was married to the wealthy Scottish heiress Anne Scott, countess of Buccleuch; they were created duke and duchess of Buccleuch, and he took the surname of Scott
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https://www.britannica.com/biography...ke-of-Monmouth
The Monmouth title was lost when he was beheaded, the Duchy of Bucchleuch was restored to his grandson, and the subsidiary titles.