Question: Whose younger brother accompanied the expedition that discovered Russia's first diamonds?

Context paragraphs:
Adolphe de Polier: Count Adolphe de Polier (1795 - 1830) was a French officer in the service of the Russian Imperial court from 1827, Chamberlain of Emperor Nicholas the Ist, he serves as vice-minister of Finance.  Member of the Russian Academy of Science he organises scientific expeditions.  During one of those in 1829 with Alexander von Humboldt, Polier discovered Russia's first diamonds.  It was the first time Russia got an indication of its tremendous rich natural resources that drives today's Russian economy.

Larry Yount: Lawrence King "Larry" Yount (born February 15, 1950 in Houston, Texas) is a former professional baseball player.  Yount (whose younger brother is Hall of Famer Robin Yount) holds the unique distinction of being the only pitcher in Major League Baseball (MLB) history to appear in the official record books without ever actually having faced a batter.  In his only major league appearance on September 15, 1971, he had to leave the game during his warm-up pitches due to injury.

Thakka Thakka: Thakka Thakka (English: "Attack Attack" ) is a 2015 Indian Tamil-language action-drama film written and directed by Sanjeev, whose younger brother, Vikranth, plays the lead role.  The film, earlier titled "Piravi", also features Rahul Venkat, Abhinaya, Leema Babu and Parvati Nirban in lead roles.  It was released worldwide by S. Thanu's Kalaipuli International on 28 August 2015.

Rogers baronets: The Rogers Baronetcy, of Wisdome in the County of Devon, was a title in the Baronetage of England.  It was created in 1699 for John Rogers, a merchant and Member of Parliament for Plymouth.  His son, the second Baronet, and grandson, the third Baronet, also represented Plymouth in Parliament.  The latter was childless and was succeeded by his younger brother, the fourth Baron.  He was a Captain in the Royal Navy.  His son, the fifth Baronet, sat as Member of Parliament for Plymouth.  He was succeeded by his eldest son, the sixth Baronet.  He sat as Member of Parliament for Callington and was also a composer.  He was unmarried and was succeeded by his younger brother, the seventh Baronet.  The latter was succeeded by his eldest son, the eighth Baronet.  He was a prominent civil servant and notably served as Permanent Under-Secretary of State for the Colonies from 1860 to 1871.  In 1871 he was elevated to the Peerage of the United Kingdom as Baron Blachford, of Wisdome and of Blachford in the County of Devon (Blachford House, Cornwood, near Ivybridge).  He died childless in 1889 when the barony became extinct.  He was succeeded in the baronetcy by his younger brother, the ninth Baronet.  The latter was in his turn succeeded by another brother, the tenth Baronet, on whose death in 1895 the baronetcy became extinct as well.

Giuseppe Pecci: Giuseppe Pecci {'1': ", '2': ", '3': 'S.J.', '4': "} (13 December 1807 – 8 February 1890) was a Catholic Thomist theologian whose younger brother, Vincenzo, became Pope Leo XIII and appointed him a cardinal.  The Neo-Thomist revival, which Leo XIII and his brother Giuseppe, Cardinal Pecci originated in 1879, remained the leading papal philosophy until Vatican II.

Alexander von Humboldt: Friedrich Wilhelm Heinrich Alexander von Humboldt (] ; 14 September 17696 May 1859) was a Prussian geographer, naturalist, explorer, and influential proponent of Romantic philosophy and science.  He was the younger brother of the Prussian minister, philosopher, and linguist Wilhelm von Humboldt (1767–1835).  Humboldt's quantitative work on botanical geography laid the foundation for the field of biogeography.  Humboldt's advocacy of long-term systematic geophysical measurement laid the foundation for modern geomagnetic and meteorological monitoring.

The Old Maid's Song: The Old Maid's Song is an American folk song.  It recounts the story of a woman whose younger sisters have married, while she has remained a spinster into middle age.  During the chorus of the song, the narrator defines a loose criterion for a husband.

Boreel baronets: The Boreel, later Boreel Baronetcy, of Amsterdam in the Netherlands, is a title in the Baronetage of England.  It was created on 21 March 1645 for William Boreel.  He was Dutch Ambassador to England, Sweden and Venice.  The title descended in the direct line until the death of his grandson, the third Baronet, in 1710.  The late Baronet died unmarried and was succeeded by his younger brother, the fourth Baronet.  He died without male issue and was succeeded by his first cousin, the fifth Baronet.  He was the son of James Boreel, younger son of the first Baronet.  He died childless and was succeeded by his nephew, the sixth Baronet.  He was the son of James Boreel, younger brother of the fifth Baronet.  He never married and was succeeded by his first cousin once removed, the seventh Baronet.  He was the grandson of John Hieronymous Boreel, younger brother of the fifth Baronet.  His son, the eighth Baronet, was created a Jonkheer in the Dutch nobility.  The title descended from father to son until the death of his grandson, the tenth Baronet, in 1937.

Ernest Wild: Henry Ernest Wild AM (10 August 1879 – 10 March 1918), known as Ernest Wild, was a British Royal Naval seaman and Antarctic explorer, a younger brother of Frank Wild.  Unlike his more renowned brother, who went south on five occasions, Ernest Wild made only a single trip to the Antarctic, as a member of the Ross Sea party in support of Sir Ernest Shackleton's Imperial Trans-Antarctic Expedition, 1914–17.  He was one of the group of ten who were stranded ashore when the expedition's ship was blown from its moorings in a gale and were forced to improvise in order to survive.  He played a full part in the party's main depot-laying journey, 1915–16, and in recognition of his efforts to save the lives of two comrades on that journey, he was posthumously awarded the Albert Medal.  Having survived the expedition, he died while on active service with the Royal Navy in the Mediterranean Sea in March 1918.

Berseba Constituency: Berseba is a constituency in the ǁKaras Region of Namibia.  Its population is 9,195, the main settlement is Berseba.  The first diamonds in Namibia were found in this area in 1898, while oil was found in 1929.  Berseba constituency contains the Brukkaros crater and the settlements of Snyfontein, Helmeringhausen, Tses, Bethanie, and Goageb.

Supporting paragraphs: Adolphe de Polier Alexander von Humboldt
Answer: Wilhelm von Humboldt