In 1781 already aged 51, Branicki contracted a strategic marriage with one of the leading members of the imperial court, Alexandra von Engelhardt, almost 25 years younger and, according to court gossip, the illegitimate daughter of Catherine the Great.
The marriage sealed the Tsarina's foothold in the Commonwealth of Two Nations, already in the process of disintegration.
The new Countess Branicka, who was inordinately close to Prince Potemkin until his death, became the Chatelaine of Biała Cerkiew amidst many other possessions across Poland and in what has now become the Ukraine.
Despite her extra-marital interest, the marriage was said to be harmonious.
Due to her business acumen and contacts, she was able to cover  her husband's colossal debts.
In return, he spent even more money in creating Alexandria, an impossibly lavish summer palace and park in her honour, making it the epitome of Polish classicism.
They had five surviving children:
Katarzyna Branicka
Aleksander Branicki
Władysław Grzegorz Branicki
Zofia Branicka
Elżbieta Branicka.

As a memorial to their children who did not survive, the couple had a waterfall and Folly constructed in the grounds of Alexandria.
In 1781 already aged 51, Branicki contracted a strategic marriage with one of the leading members of the imperial court, Alexandra von Engelhardt, almost 25 years younger and, according to court gossip, the illegitimate daughter of Catherine the Great. The marriage sealed the Tsarina's foothold in the Commonwealth of Two Nations, already in the process of disintegration. The new Countess Branicka, who was inordinately close to Prince Potemkin until his death, became the Chatelaine of Biała Cerkiew amidst many other possessions across Poland and in what has now become the Ukraine. Despite her extra-marital interest, the marriage was said to be harmonious. Due to her business acumen and contacts, she was able to cover  her husband's colossal debts. In return, he spent even more money in creating Alexandria, an impossibly lavish summer palace and park in her honour, making it the epitome of Polish classicism. They had five surviving children:
Katarzyna Branicka
Aleksander Branicki
Władysław Grzegorz Branicki
Zofia Branicka
Elżbieta Branicka. 
As a memorial to their children who did not survive, the couple had a waterfall and Folly constructed in the grounds of Alexandria.
Franciszek Ksawery Branicki