No, they were never told that they were like siblings , luffy or nami didn't say anything like that, that's your opinion but it's not true

Her *

They never said they saw each other that way, you have no evidence of that, they are not like siblings

No him really read the manga

What is the joke? The spin-off series titled "One Piece in Love" has been published since 2018 as an officially recognized derivative with the approval is Oda.

You do not know Oda very well; he mentioned that he is afraid of the fans, expressed his desire to do romance, but stated that he is concerned about the possible reactions.

Firstly, no, luffy x nami is the most popular ship and they don't see each other as siblings, it's not canon, you don't have evidence of that

Lol even in japan luffy x nami comes first in the polls   

No, Luffy has already rejected him twice 

Luffy rejected him twice, something one-sided doesn't make it perfect, stop forcing it

Romance can be covered even if it's not the main subject, and what difference does it make if they're like family? They don't see each other as siblings 

What sworn are you talking about?  Luffy rejected him twice.