Willem Mons was the brother of Peter the Great's long-time mistress Anna Mons

Anna Mons

Anna Mons was a German commonner who almost succeeded in marrying Tsar Peter the Great.- Biography :In 1691, during one of his visits to the German Quarter, young Peter I of Russia became enamoured of Anna Mons, the daughter of Dutch wine merchant Johann Mon. It is generally thought he was from...

, who later served as private secretary to his wife Catherine

Catherine I of Russia

Catherine I , the second wife of Peter the Great, reigned as Empress of Russia from 1725 until her death.-Life as a peasant woman:The life of Catherine I was said by Voltaire to be nearly as extraordinary as that of Peter the Great himself. There are no documents that confirm her origins. Born on...

.

After his sister's fall from favour, Willem joined the Russian army and took part in the Battle of Poltava

Battle of Poltava

The Battle of Poltava on 27 June 1709 was the decisive victory of Peter I of Russia over the Swedish forces under Field Marshal Carl Gustav Rehnskiöld in one of the battles of the Great Northern War. It is widely believed to have been the beginning of Sweden's decline as a Great Power; the...

. In 1711, he was appointed personal adjutant to the tsar. His other sister Matryona Balk had in the meantime become the closest friend of Catherine, whom Peter married in 1712.

In 1716, at Catherine's behest, Peter entrusted Willem with administering her estates. After Catherine's coronation as consort in 1724, he was promoted to the rank of imperial chamberlain

Chamberlain (office)

A chamberlain is an officer in charge of managing a household. In many countries there are ceremonial posts associated with the household of the sovereign....

. A few months later, however, Willem Mons was arrested on charges of peculation (embezzlement

Embezzlement

Embezzlement is the act of dishonestly appropriating or secreting assets by one or more individuals to whom such assets have been entrusted....

) and breach of trust and, after a brief and brutal inquiry by Pyotr Tolstoy, he was publicly drawn and quartered on November 16. His head was preserved in alcohol and is still kept in the Kunstkamera

Kunstkamera

The Kunstkamera was the first museum in Russia. Established by Peter the Great and completed in 1727, the Kunstkammer Building hosts the Peter the Great Museum of Anthropology and Ethnography, with a collection of almost 2,000,000 items...

. There is a legend that Peter forced his wife to contemplate this gruesome exhibit for hours.

The true causes of Willem's downfall are obscure. It was rumoured that Peter was enraged by his intimacy with the Empress. Many courtiers regarded Mons as Catherine's lover and his sister Matryona as their matchmaker. The affair did not affect Catherine's position as empress, however.

Just months after his execution, she succeeded to the throne and lavished honours on Matryona (who had been publicly flogged during her brother's trial) and her Lutheran daughter, Natalia Lopukhina

Natalia Lopukhina

Natalia Fyodorovna Lopukhina was a daughter of Matryona Balk, who was sister of Anna Mons and Willem Mons. She is famous for the Lopukhina Affair, an alleged conspiracy engineered by the diplomacy of Holstein and France at the Russian court and centered on the person of Lopukhina.During the reign...

, who would later give her name to the Lopukhina Conspiracy (1742–43).