>>530079031
Non-blood related foster sister breeding is extremely encouraged in China from what I have seen.

They want you to accept your girlfriend/wife as your treasured sister.
But they don't like the inbreeding aspects of sister mating, it it turn into a game of roleplaying where your girlfriends call you "big brother". You adopt a stranger as your sister an i ncourag to breed her like only an older brother can do.