Good arguments about the relationship between Nemu and Junichi. I guess 90% of this is perty much left up to the person viewing things. For example, cousin marrage in Japan is legal. In the states anything short of a relative twice removed on down to total stranger will get you linched. IF there is ANY hint that the said person person MIGHT be related to you, oh brother. Watchout for the backlash. In Japan that's not the case. Sister and bother? Uh, that's a given that it's a no-no perty much everywhere. The rest is left up to culture.
I'm more one to lean towards Junichi not being allowed to date either Nemu or Sakura. Reason I say that is, Sakura is his cousin. Nemu is his sister, be it by law (adoption) or by blood, once she becomes a part of the family, she ceases to be fair game on the dating scene for anyone in the family. That's just my two cents.
Now as an outsider looking in, I'd date either Nemu or Sakura in the drop of a hat.
