[3] Pyotr enlisted in the Preobrazhensky Regiment as a child and from 1722 to 1727 served under the young Charles Frederick, Duke of Holstein-Gottorp (1700-1739) as a page, Kammerpage and finally lieutenant-captain.
[5] Next, in 1746, he was posted to London, assisting at the Congress of Aix-la-Chapelle at the end of the War of the Austrian Succession between April and October 1748.
[5] Count Chernyshev married Ekaterina Chernysheva (1715–1779), the daughter of Andrei Ushakov [ru].
Together, they were the parents of:[6] Count Chernyshev died of dropsy in Saint Petersburg and was buried at the Alexander Nevsky Lavra in the Lazarevskoe Cemetery.
[10] His tomb inscription reads "His life was cut short by multiplying diseases, to the extreme sorrow of his neighbours and to the sincere grief of his friends and admirers".