And throughout scripture these words are also used for relationships which have nothing to do with literal brotherhood.
You've allowed yourself to be blinded by 'context', otherwise known as 'your own agenda'.
Please see Matthew 4:18
Now as Jesus was walking by the Sea of Galilee, He saw two brothers, Simon who was called Peter, and Andrew his brother, casting a net into the sea; for they were fishermen.
Are Peter and Andrew brothers by the same parents or just relationships which have "nothing to do with literal brotherhood?"
Guess which word is used to denote brothers?
ἀδελφούς
It is plural of ἀδελφός, brother.
Context tells you Simon and Andrew are blood brothers from the same parents.
Matthew 10:2
These are the names of the twelve apostles: first, Simon (who is called Peter) and his brother Andrew; James son of Zebedee, and his brother John;
Guess which Greek is used here?
So no....this is not my agenda. My agenda is to help you understand that context is the key to understanding a passage.
You have to look at more than just one word. How is it used in context? Is it indicating possession? Is it an adjective?
What are the verbs indicating in the passage.
Without knowing the Greek behind it you cannot really understand the finer points the writer(s) are making.
I hope this helps in your understanding of the Word.
For instance:
Was Jonathan was the literal brother of David?
Was Lot was the literal brother of Abraham?
Indeed not. These words are used to denote a huge range of familial and non-familial relationships. It would be insane (for instance) to insist that Jesus had literal brothers simply because a word that usually doesn't mean literal brother is used.