Complex sentence: They then sold it onto the Cary family in 1348, who then sold it to the Mallock family in 1645, a family of rich silversmiths from Exeter.
Split into simpler sentences: They then sold it onto the Cary family in 1348. The Cary family then sold it to the Mallock family in 1645, who where a family of rich silversmiths from Exeter.