And throughout scripture these words are also used for relationships which have nothing to do with literal brotherhood.
Just because adelphos and adelphoi are used to denote literal brotherhood for Peter and Andrew, this doesn't mean that these words must always be translated in the same way.
I agree. That's why context is your key to understanding the Word.
You're attempting to equate a Greek word with a Hebrew word.
Let's stay with the Greek for now.
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.
Why would it be insane for Jesus to have brothers and sisters?
46While He was still speaking to the crowds, behold, His mother and brothers were standing outside, seeking to speak to Him. 47Someone said to Him, “Behold, Your mother and Your brothers are standing outside seeking to speak to You.” Matthew 12:46-47.
The people who were at this event recognized that these were the brothers of Jesus....your mother....your brothers.
This translation is just as good, given the multiple meanings in scripture:
"Behold your Mother and your family are standing outside seeking to speak to You"