He was born in Christiania as the son of merchant Johannes Thomassen Heftye (1792–1856) Tina Haslef (1798–1862).
[1] Through his daughter Ingeborg Marie he was a father-in-law of Frits Hansen[2] and grandfather of Eilif Fougner.
[1] His grandfather migrated to Norway from Switzerland in the late eighteenth century, and founded the family company Thos.
He also financed writers and artists such as Aasmund Olavson Vinje, Bjørnstjerne Bjørnson, Hans Gude and P. A.
The reason why he changed from Aker to Christiania after 1877 was that Frogner, where he lived, was incorporated into the city in 1878.
[1] A memorial stone was raised for him at Midtstuen, and the road Thomas Heftyes gate [no] in Frogner, Oslo has been named after him.