Complex sentence: On the death of Sir John Wynn in 1719, his heiress Jane Thelwall inherited the Wynnstay estate and his claim to Aberffraw, and her husband Watkins Williams added the Wynn family name to his own.
Split into simpler sentences: On the death of Sir John Wynn in 1719, his heiress Jane Thelwall inherited both the Wynnstay estate and the Wynn claim to Aberffraw. Her husband Watkin Williams then added the Wynn family name to his own.