I understand your point of view, but that doesn't mean my background doesn't inform my perspective. As I mentioned if I hear someone call another brother, even when adding "big" to it as a qualifier, I don't automatically assume they are biological brothers. There are all sorts of situations where that can happen. Heck, there is a even a mentoring program called "Big Brothers Big Sisters" I used to be involved with where the mentor/mentee would regularly call each other big brother/little brother in conversation.
So agree to disagree on that. But I hope this helps you understand why my background helps color my opinion.
And I agree those are valid examples on how one would conclude that biological link. I'm just not conceding that its not possible to also conclude that its a non-biological link. Which is why I leave it up to the original intent of the filmmakers, they are the final authority on it in my opinion. If you disagree with the filmmakers and say that should have made it more clear in the original if that is what they intended, well that is up to you.