Really hard to explain this one

i bought d2r 17th of september or october.
at the time im not sure if my xbox-battle,net was linked but anyways,
i bought the game and i could play it.
Yesterday, 27th of November, my brother bought d2r for xbox but,
whenever he is playing
and i launch d2r on pc which i bought separately,
he gets kicked out.
This feels like i bought the game for pc and now i can play it on xbox too but you cant because you only buy it for a certain platform, right?
So how does this make any sense?
He should be able to play his own game, why cant i play the game at the same time?

Keep in mind:
WE BOUGHT SEPARATELY ON SEPARATE PLATFORMS,
WE USE DiFFERENT CHARACTERS.

And i just dont see how does that make anysense.

As for crossprogression yes you cant play crossplatform and the same character at the same time, it totally makes sense, but we should be able to play the game at the same time because we bought it separately and ye its hard to make a point. im having trouble with english.

We both paid 40 euros so we could not play our own game?
you get me?
i bought it for pc for 40 euros and we couldnt play it on xbox because you have to buy it for the XBOX but then we should be able to play at the same time, and i dont mean same server and stuff i mean just play with our own online characters because everyone who buys the game can play it, right?

As you say they are 2 separate platforms, so separating them should then allow your brother to connect to XBOX and yourself on PC at the same time.

If you navigate to the Account Connections in Account Management, you should be able to remove the link to XBOX Live.