I write "subculture", because they exist in many different cultures. Perhaps literally everywhere where voluntary low birth rate happens at all. (I don't know of a breeder subculture in Japan, but I'd be surprised if it did not exist. We certainly do have them here in Germany, and they scare the shit out of regular people in the rural regions they colonize, with their "everything Nazi except the Hakenkreuz")
Back to end game: the current set of what people consider human rights ("have children and raise them however you like") seems to make it inevitable that those subcultures thrive until they aren't sub anymore. Participate in the breeding race or you're out. It's almost as if back when they declared human rights they accidentally enshrined the very foundation of Nazi ideology when they tried to keep that from happening ever again.
But then on the other hand, the actual text of the declaration makes very little mention of procreation. All those who cry "but human rights!" whenever the topic comes up seem to base their argument on (or be mislead by, I guess most seem to assume that it's a straight forward article resembling "go forth and multiply", I know I did before looking it up). I'd love to see some discussion of de-sanctifying the presumed right to "sire and ideologize an army" (I wish I was exaggerating..) before things get so ugly that the discussion will include radical swings of the pendulum to the other side. Perhaps a viable diplomatic approach could be more explicit protection for the first two children, and in exchange less article 26.3 beyond that threshold? We certainly should not try to actively solve breeder subcultures, but we should give them less to hide behind.