The baptism of Maria Oldecop in 1782 was witnessed by a Russian Grand Duchess

In Amsterdam on Thursday January 20, 1774, Johan Hendrik Frederik Oldecop, 37 years old and living near the Binnen-Amstel, promised to marry 24-year-old Helena Paauw. Her mother, Susanna Alles, had given permission for the marriage. Both the bride and groom were Lutheran, and lived in Amsterdam.
At some point, Johan Hendrik Frederik van Oldecop was appointed consul of the Russian Emperor in Amsterdam.

The couple had several children with notable witnesses at their baptisms:

Prince Alexander Kurakin
(1752-1818)

1. Jan Hendrik was baptised on 27 March 1769 with witnesses Daniel Butler and Maria Hoogstraten. The child Jan Hendrik, who is listed in the baptismal register as Jan Hendrik Fredriksz, is the son of Jan Hendrik Frederik van Oldecop and Helena Paauw.
2. Helena Adelaide was baptised on 3 September 1773 with witnesses Prince Dmitri Alekseyevich Golitsyn (1728–1803), ambassador to Holland, and his wife Gräfin Adelheid Amelie von Schmettau (1748-1806).
3. Michel Daniel was baptised on 14 March 1775 with witnesses Michel, Prince Volkonsky, and Elisabeth, Princess Volkonsky.
4. Iwan was baptised on 13 April 1776 with witness Iwan Czernichew.
5. Benine Alexandrine was baptised on 3 October 1777 with witness Prince Alexander Kourakin (1752-1818). She married Etienne Carignani on 8 January 1801 in Moscow.
6. Helena Catharina Anna was baptised on 30 April 1779 with witnesses Count Gregory Orlov (1734–83) and his wife Ekaterina Zinnovyeva. In 1800 she married Jacobus Heydanus. In March 1848 items from her inheritance were offered for sale.
7. Maria was baptised on 23 October 1780 with witness Grand Duchess Maria Feodorowna of Russia. Maria died young.
8. Maria was baptised on 5 July 1782 with witness Grand Duchess Maria Fedorowna of Russia. At the age of 21, Maria died from measles in 1803 in St. Petersburg.
9. Helena was baptised on 6 August 1783 with witness Prince "Wiasemskoij" (possibly Vyazemsky) and his wife. In 1810 Helena Oldecop married Samuel Rondeau junior. They had issue. Helena died on 25 January 1859 in Amsterdam, aged 75.
10. Paul is mentioned in May 1791.
11. Etienette was born around 1787 in Haarlem. She married widower Johannes Foon, but she survived both him, and their son Jan Hendrik Frederik Foon. As a widow, Etiennette ran a boarding school for girls in Loenen. Etienette was 49 years old when died on 21 March 1836 in Maarsseveen near Utrecht.

Maria Oldecop was baptised on 15 July 1782 in Amsterdam.
The witness was Maria Feodorovna, Grand Duchess of Russia.

Grand Duchess Maria Feodorovna (1759-1828) was born as Sophie Dorothea of Württemberg, but changed her name when she converted to the Russian Orthodox Church, and married Paul of Russia as his second wife. She was Empress Consort during her husband's reign, which lasted from 1796 until his assassination in 1801.

Despite an imperial witness, Maria Oldecop died of measles in St. Petersburg, Russia, in 1803 at the age of 21.

Amsterdamse Courant (newspaper), 1 December 1803

The burial of Johan Hendrik Frederik van Oldecop was registered in Amsterdam on 9 January 1789. His widow and children were mentioned in May 1791.
At the age of 66, after long and painful suffering, Helena Paauw died in Weesp on 30 July 1816 around 4 A.M. She was survived by 3 daughters.

Opregte Haarlemsche Courant (newspaper), 3 August 1816

Sources: Delpher.nl, WieWasWie.nl, Archief.Amsterdam website, Noord-HollandsArchief.nl, and the Wikipedia pages of the Kurakin, von Schmettau, Volonksy and Orlov families.