Bridgerton season 1 includes a subplot involving Prince Frederick of Prussia, but the character isn't entirely historically accurate. Portrayed by Freddie Stroma, Frederick is identified as the nephew of Queen Charlotte (Golda Rosheuvel) and tries to capture the heart of Daphne Bridgerton (Phoebe Dynevor). While an interesting addition to the show, the real life details of the Prince in this time period are far different.
Prince Frederick of Prussia appears in three episodes of Bridgerton season 1. In "Art of the Swoon," the character arrives at a party and immediately takes a liking to Cressida Cowper (Jessica Madsen), which prompts a comedic social commentary from Daphne and her faux boyfriend, Simon Basset (Regé-Jean Page), the Duke of Hastings. Later, Frederick has a proper conversation with Daphne, who is distracted upon spotting Simon and urges the Prince to "make the rounds" and enjoy time with "a gaggle of young ladies." As the Duke becomes less accessible during the London season in Bridgerton season 1, Daphne decides to manipulate her situation by flirting with her new friend from Prussia.
For dramatic purposes, Prince Frederick of Prussia exists in Bridgerton season 1 to boosts the central love story between Daphne and the Duke, who becomes increasingly jealous while refusing to admit his true feelings. In 1803 - the setting of Bridgerton season 1 - the real-life Prince was just nine years old and lived in Berlin, Germany (the Kingdom of Prussia). In 1814, 20-year-old Frederick was romantically linked to Princess Charlotte of Wales, the granddaughter of King George III, which seems to be the narrative inspiration for the character's fictional familial ties to Queen Charlotte - the wife of King George III.
The historic Prince Frederick of Prussia married Princess Louise of Anhalt-Bernburg in 1817. At that time, he'd been commanding the 1st Life Cuirassiers regiment of the Royal Prussian Army, which means that he would've been traveling extensively, as Phoebe references in Bridgerton season 1. In fact, Prince Frederick actually led the cavalry for nearly 50 years, and became a well-known patron of the arts while living at Jägerhof Castle.
The Prince of Prussia's real-life story also notably links thematically with the Duke of Hastings in Bridgerton. In real life, Frederick had two sons - Alexander and George - both of whom were military officers and strengthened the family's legacy. But even though Alexander lived to be 75 years old, he never sired a son of his own to extend the bloodline. Similarly, George - a respected poet - lived to be 76 years old but also didn't have a son. In Bridgerton season 1, the Duke of Hastings informs his dying father that he will never have a child out of pure spite; the result of being rejected as a child because of an embarrassing stammer.