Yukasumi wouldn't be but if renko is a direct descendant then renmari would be incest since Mary would be renko's great something grandmother.
FatherMotherYakumo YukariUsami SumirekoMaribel HearnUsami RenkoYay!Age of Science※ This is a original setting.Through iPS cells children can be born even between people of the same sex!!Thanks iPS cells
Thanks YukaSumiSame-sex marriage is the obvious choice! Yay!!RenMari Chu Chu!