Sorry for interfering, butl there is always room for explanation why they're not siblings - perhaps their parents were close friends and died in the same accident. Or maybe it was some kind of crime story in WIAB that both their families were victims of.
No matter if they are not related or just not aware of it,. None of this explains why they talk like brother and sister who simply replaced the words "bro", "sister", "sibling" with "friend". Many phrases in the game do not make much sense until you replace a friend with a sibling. Bella approves MC who confirmed he'll help Nami get revenge: "That's what I expected. They help each other, they stay by each other's side no matter what happens." Who are they? I'm pretty sure the "siblings" word were there before the fourth chapter has been released. Vanessa to Nami: "Your body is a temple, Nami. He might be MC, but every male should honor it". Maybe I'm missing something there, but this phrase sounds wierd until you replace "He might be MC" with "He might be your brother". There are many other similar wierd phrases be found across the game.
These changes in SG and WIAB are just because of Patreon´s bigotry. This is even more obvious in old WIAB. Some dialog there is hilarious once Ocean had to change the game to keep Patreon of his neck! There is e.g. a conversation between Willi and Leia which is in effect satirical after rework. Once you insert "twin(s)" and "brother/sister" it is fine, instead of "bestest roommate forever" and stuff.
Another example from old WIAB: There is a "truth or Dare" game where the MC is asked which one of his "friends" he would bang if he had or would want to. The ONLY choices are Leia and Kati! Conspiciously absent are his girlfriend(!) Miru, old friends like Zoey or Dana. And when you answer Leia, Dana exclaims that the legends are true.
And you can even see that in new WIAB. When you meet Leia outside the house, the conversation with her and Miru makes much more sense if you insert twin or sister, as the patch does.
As for Summer´s gone, one of the biggest hints that MC and Nami are really siblings are the numerous talks about how she can be a redhead. That makes zero sense if they were from two different families adpoted at the same time. It would be a non-topic since they would come from different family lines, with Nami coming from a family with supposedly many redheads. But the questions about her haircolour make it clear that she comes from a family with nearly none or no history of redheads in them.
