Need advice

[Threigia]

What is the name of your state? Arizona

There is no easy way to ask this, but is there a way for two adults to adopt each other legally as siblings? I ask this due to the fact that one of my dearest friends and I have started seeing each other as siblings, and in some ways we are closer to each other than to our birth families.
Is there a way to do this, or do I go through life saying "I'd like you to meet my friend" when it feels like I should be saying "I'd like you to meet my brother"?

[nextwife]

No, siblings cannot adopt a sibling.

The Adoptor is a parent, adopting a child, even an adult child. You can ONLY use adoption to become siblings IF one or the other has a living parent that adopts the other.

But that would make the adoptee NO LONGER the "child" of their bioparent.