He was the second son of the future King Gustaf VI Adolf and his first wife, Princess Margaret of Connaught, eldest daughter of Prince Arthur, Duke of Connaught and Strathearn and granddaughter of Britain's Queen Victoria. He was a Prince of Sweden from birth, but was excluded from the line of succession in 1934 when he married a woman of unequal rank, a violation of provisions prohibiting marriages between a Prince and a "private man's daughter" (), in force at the time, contained in both the 1809 Instrument of Government and the 1810 Act of Succession, and, in addition, he lost his princely and ducal titles as decided by the King in Council. As per the king's wishes he was then to be called only "Mr. Sigvard Bernadotte" in Sweden. In 1951 he was granted Luxembourgian titles of nobility, the interpretation of which remained a point of contention with the Royal Court for the rest of his life, Bernadotte having formally declared in 1983 that his title was Prince Sigvard Bernadotte.