This argument is one one the most insane things I've heard repeatedly in my life. There is not a single shred of logical thinking behind this. Blood does matter. Whether you're raised together or not doesn't matter at all. One has serious medical/biological implications for offspring. The other has no effect whatsoever on any aspect of your life.
Well, yes, for offspring does matter. But that's it.
So unless you are telling me MC has knocked Nami up, it makes no difference.
Anyway, I think you missed my point. I was talking about their relationship, not whether they are planning a life with kids.
Also, if blood-related, they could adopt, so no biggie either.
I was in this camp too. The fact they are so different...maybe Ocean wants to keep people guessing. Or have enough leeway to switch things around, maybe introduce a twist later on. As I see it the game makes very little sense if they aren't blood related. Plus the bond between Nami and the MC that sustains so much of the narrative is severely weakened if they turned out to not be related in my opinion.
There is a reason you don't see anyone asking MC and Nami "why are you white?" after seeing Nojiko...
The bond thing is not true. Adoptive siblings are as close as blood related.
The thing about her hair color does suggest blood related. Although if not siblings, MC knew her parents and they could be non redheads. Not supporting this, simply giving a possible explanation for an unlikely scenario