Dimitri von Leuschner Frankie Brady

I have seen on a fandom for this show, the character of Frankie Brady is Dimitri’s paternal cousin, Frankie’s biological father, Henri, was only seen in flashbacks, I kind of doubt that in those flashbacks showed Henri’s siblings, so if in those flashbacks that it was never shown of Hank’s siblings, how could anyone of them be Dimitri’s father or mother, to explain Dimitri being Henri’s nephew, Frankie’s cousin?