cahn

And the uncle/niece marriage was still way more functional than the one of that girl's parents. I mean, due to being the youngest of the FW/SD brood, Ferdinand was only eight years older than his niece. (He was born in 1730, the year of doom.) (Something to keep in mind about SD, too, of course, that she was pregnant during some of that year, though by the time Fritz tried to escape baby Ferdinand was already there.) And they actually got along. Meanwhile, his poor older sister Sophie had been married to that same 19 years older Margrave of Schwedt whom Wilhelmine absolutely did not want (nicknamed "the mad Margrave" for good reason), and then, according to Wiki: The relationship of the couple was not happy. Sophia often fled to the protection of her brother King Frederick. The latter did not stop at friendly admonitions, but sent General Meir to Schwedt with unlimited authority to protect the margravine from insult. Eventually they lived in separate places: Sophia lived in the castle Montplaisir, and the Margrave lived in the castle of Schwedt.

Go Fritz, I suppose? Doing something nice for a sibling who isn't Wilhelmine? On the other hand, Wiki also says, re: Fritz and this brother-in-law in general (who was also his cousin): In contrast to his father's policy Frederick II sought to distance himself from his Schwedt cousins, humiliating them at every chance. He made them unwelcome at his court, undermined the margrave's authority in his own dominions by encouraging complaints and lawsuits by his tenants and neighbours and, most effectively, he marginalised the position of the Schwedt brothers within the Prussian army. Margrave Frederick William was removed from command in the army.

....Yeah, Elisabeth Luise (aka the niece) sure grew up in a peaceful family atmosphere, alright.