https://www.dlsite.com/books/work/=/product_id/BJ515304.html
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Impregnate me with your brother's cock! My mother, my sister and my aunt are all over my cock!

A law is passed to make close-kin relationships legal, and Yuumi, who loves her brother, tries to keep his dick to herself to keep her mother and aunt from slipping out...

I knew I had seen this one before but I couldn't find it by the author name:
JP: /g/2204934/060eae43eb/
EN: /g/2432006/745917e54f/
Tagged the author in those galleries now, though I need more power.
Now the real question is where's the chapter focusing on the two from the beginning? I need that long black hair big sister.

Base +8, Fofotron +10, eternallifecat +6

p. 44 has censored "フェラ"

Base +7