I just wanted to go over some slang terms for friend (m/f) and sibling (m/f) in Portuguese. There’s not much to it as the title of the post pretty much says it all.
Mano or Maninho can mean brother or friend, interchangably. Equally so, Mana or Maninha can mean sister or friend. If used to mean sibling, it’s not at all uncommon to see these terms used rather than the traditional irmão/irmã. If I had to choose one of the four terms mentioned as the one used the least, I would say ‘mana’ isn’t so popular as a way to say (female) friend. As far as saying friend, there are many ways, as I mentioned in my Tricky Verbs & Words 5 post. If in doubt though, just use amigo/amiga.
Portuguese has no gender neutral term such as the English ‘sibling’. See comments for a little more on ‘mano’ as friend.