Okay so from day one, Prussia has been my favourite Hetalia character. No if's, and's, or but's about it. Though she hasn't been about as long, NyoPrussia has been just as dear to me from the moment she made her debut.
Something about this absolute goober just captured my heart from the first time I watched this dumb weeb shit. I am still obsessed. I will never not be obsessed. If Hetalia, and by extension Prussia and NyoPrussia have no fans, I am dead.
They've been a lot of things to me over the years, whatever I've needed at any given time. We're in love. We're best friends. We're siblings. Husband and Wife and Wife. Platonic life partners. They sit on the cuck couch when a new character catches my attention. Strictly duogamous. It's an open relationship. Trine. Blorbos from my show.
Prussia (Gilbert Beilschmidt) and his alternate universe Nyotalia counterpart Nyo!Prussia (Maria Beilschmidt) are characters from the still ongoing webcomic turned manga turned anime turned Nintendo DS game turned musical stage production "Hetalia"; aka if polandball comics had pretty anime boys and girls, and the superior version of countryhumans.
The characters themselves within the timeline of the series started out as the human manifestation of the Teutonic Order, and later became the Duchy/Kingdom of Prussia, and eventually East Germany. Currently, they're retired and just doing whatever they please.
Prussia's first appearance was in the Maria Theresa and The War Of Austrian Succession comic strip in 2007, which was adapted for Volume 1 of the manga. His debut anime episode is Season 1(Axis Powers) Episode 10. Nyo Prussia appears first appears on Himaruya's Bamboo Thicket blog thicket blog before making her anime appearance in Season 5 (Beautiful World) Extra Episode 5, which was adapted from the Axis Powers Volume 4 strip I Was Overwhelmed by Heroines, which interestingly enough she does not appear in.
Also of note is that there are an additional two variations of these characters- the 2P/"Another Colour" versions, however only Nyo!Prussia has an official 2P design.
Their family tree is convoluted and frankly makes little sense and is better off being considered non literal. Prussia is Germany's older sibling, and Germania is their parent, who was dead for centuries before Germany's non-birth (and probably Prussia's too (unless you want to get non canonical and assume his true origins were with the Old Prussians(which only would raise more questions about genealogy))) where he was willed into existence(Or perhaps resurrected from a preexisting body?) as a young child rather than a baby by all the German states coming together under Bismark to form the German Empire. The Holy Roman Empire (Deceased, possibly the aforementioned dead body) is also one of Germania's children, and thus a sibling to them, but would technically be older than Prussia. Switzerland and Liechtenstein are also relatives, probably cousins or something. Saxony, Bavaria, and Hesse are the only other siblings depicted and identified, though Brandenburg and Holstein are also mentioned by name, it's safe to assume pretty much any state that eventually became part of the German Empire is considered a sibling.