As you can see there is some confusion here. I hope this helps you figure it out.
A friend had this to say: "my Grandmother was Isabelle Hofmeyer, kin (Niece - I think) to Jan Hendrik Hofmeyer (Tvl Administrator) who was also cousin to Jannie Smuts. Her brothers were also Willie Hofmeyer (SWA Admin ) and Hoffie Hofmeyer ( Min of Traditional Affairs)".
A brief search gave me a Jan Hendrik Hofmeyr-"Onze Jan" (4 July 1845 – 11 October 1909), a South African politician.
He was a Member of the Cape House of Assembly for Stellenbosch. In office: 1879 – 11 October 1909 & Minister without portfolio. In office: May – November 1881.
He had a nephew, Jan Hendrik Hofmeyr. Baptised Jan Frederick Hendrik Hofmeyr, but he dropped the name Frederick & was also known as "Hoffie", (diminutive form of his surname).
Administrator of the Transvaal. In office: 1924–1929.
Minister of Finance and Education. In office: 5 September 1939 – 25 May 1948.
Deputy Prime Minister. In office
Born: 20 March 1894
Cape Town, Cape Colony
Died: 3 December 1948 (aged 54)
Johannesburg, South Africa.
Nationality: South African
Political party: South African Party, United Party.