It’s based on it. GRRM is an expert on the War of the Roses. But while the book series was ground-breaking, sublime, powerful...the HBO series was pure HBO crap, what with the fake, unconvincing, boring sex scenes, and the fact that everything that happens on the screen is blatantly about who’s having fake, unconvincing HBO sex with whom, instead of a life-and-death struggle for power amid sorcery, strange meteorology, and some sex, too, that the books were. After getting midway through the second season, I erased it all from my hard drive.
Used to play Kingmaker board game in my younger days........Based on War of the Roses...........