Amherst's mother was Mary, daughter of Andrew Fountaine, of Narford Hall, Norfolk. In 1852, he and his father assumed by Royal licence the surname of Tyssen-Amhurst.
Mary, Amherst's mother and daughter of Andrew Fountaine from Narford Hall in Norfolk, changed their family name to Tyssen-Amhurst in 1852 after receiving a royal license for the change.