(1) Sveriges Adels kalender 1908, (2) Family papers, (3) www.thepeerage.com
(4) Text from portrait engraving, (5) London Times and other information provided courtesy of David E. Cooper, Auckland, New Zealand

Name
Oscar (Oskar) Gustaf (Gustav) von Heidenstam
Date & Place Of Birth
December 31st, 1840 (1) Athens, Greece
Known Domiciles
Alexandria, Egypt
Rio de Janeiro, Brazil
Constantinople, Ottoman Turkey
Villa Bergabo, Djurgården, Stockholm, Sweden (1)
Known Occupations
Attache, Swedish Legation, Athens (1868) (5)
Chancellor, Secretary Swedish Legation, Athens (1873) (5)
Swedish Envoy, Constantinople (c.1876 to 1883) (2) (5)
Swedish Consul-General, Alexandiria, Egypt (1883-1887) (5)
Swedish-Norwegian Consul-General in Rio de Janeiro (1887-1892) (1) (5)
Vice Chairman of the Swedish Export Association (from 1892 for many years) (5)
President de l'Alliance Française de Stockholm c.1931 (4)
Contributor to The Times of London, the Revue des Deux Mondes and the Revue de Paris (5)
Immediate Family
Parents: Carl Peter von Heidenstam, Eliza Skene (3)
Spouse: Leila Jessie Boyd (1) (2)
Children: Carl Gerhard, Rolf Magnus (1) (and deceased first daughter, name unknown)
Date & Place Of Death
March 23rd, 1933, Stockholm, Sweden
Notes
Oscar Gustaf married Leila Jessie October 27th, 1875 (1). He was the author of "Swedish Life In Town And Country", published in English in 1904, "Marie-Antoinette Fersen & Barnave. Leur Correspondance" published in French in 1913. Won the Prix d'Alliance Francaise in 1914. He had the honorific "Kammarherre" or Chamberlain to the Swedish Court and also held the Order of Commander of the Vasa (5). His 1933 obituary from the London Times can be found here.