My brother and I bought the limited collector’s edition of halo 5. My question is: If I redeem the code with my account , could he play the game with his own account? (I mean, without main loged in)
Do you mean if you install it with your account signed in at the time?
Yes!
I really don’t see there being a problem. As far as I know, all content purchased by a user on an console is usable by any other GT signed in to said console. Unless 343i has done something different and in that case, someone please correct me.
the reason of why I ask is, precisely, cuz’ he wantted to play but a message of “you need to purchase the game” appear at the time 
You should be able. Every single game I have installed in my Xbox can be played by my brother and every single other account.
Maybe you have to refresh your rights stored in the console?
how can i do that?
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> My brother and I bought the limited collector’s edition of halo 5. My question is: If I redeem the code with my account , could he play the game with his own account? (I mean, without main loged in)
yes if you play on that one console the dlc should work for both with no problem 
CHECK THIS. This will explain how to set your Xbox as your “home Xbox”, you should be able to share games and DLCs stored in that home Xbox.
If problem still persists, contact Xbox Support at the bottom.
You should be fine,but i know i am having an issue doing this since one of my xbox’s is on NXOE and the other isnt.
So if you are in the same boat, u might have issues.
Just an FYI…
thxs to everyone!