[3] He resides at Schloss Berleburg-Wittgenstein in the town of Bad Berleburg, in North Rhine-Westphalia, Germany.

[3] If Gustav were to die without legitimate issue, the family heritage would devolve upon his father's younger brother, Prince Robin zu Sayn-Wittgenstein-Berleburg.

[1] Gustav was formerly engaged to be married to Elvire Pasté de Rochefort (granddaughter of French Ambassador André Rodocanachi and wife Nada Diplarakou, herself sister of Aliki Diplarakou and grand-aunt of Princess Sibilla of Luxembourg); the engagement was announced on 16 August 2000 and the wedding planned for 12 May 2001 in Paris.

However the wedding did not take place, reportedly due to financial issues with the bride's family, and it was announced on 16 July 2001 that they had separated.

[4] The couple's son, Prince Gustav Albrecht, was born on 26 May 2023 in the United States via surrogacy.