Roi Octopath - Tumblr Posts

To the Octopath Traveler 2 fandom, I need help in answering a question I have.

What is Temenos’ relation to Roi?

I have seen a lot of recent fics and fanart that are tagging/indicating that they are siblings. But is that canon or fanon?

The only mention I have seen to this question’s answer was Temenos referring to Roi as a friend in a travel banter.

Which is it?

Edit: I have been informed that they are adopted siblings. Now we know!