In 1765 John Carnac married Elizabeth Woollaston. Then in 1769 he married
Elizabeth Catherine Rivett (1751–80), daughter of
Thomas Rivett (1713–63), who had been an MP and Mayor of Derby. A 1775–76 portrait of Mrs. Carnac by
Sir Joshua Reynolds hangs in the Wallace Collection in London; with a proof impression at the British Museum. John Carnac's last will and testament made his brother-in-law James Rivett his heir, provided that he assumed the additional name of Carnac, which he did in 1801. Two of James's sons became famous: Sir
James Rivett-Carnac, 1st Bt, became a Governor of
Bombay Presidency, while Admiral
John Rivett-Carnac became an early explorer of Australia, where
Carnac Island was named in his honor by Captain
James Stirling when Rivett-Carnac was first lieutenant on on the
Swan River expedition of 1827. ==References==