How many accounts can access a particular game simultaneously?

You cant

You MUST SIGN INTO the xbox account to download the content onto the pc

Then your brother must sign out and onto his own profile to play

A PROFILE can only be signed into one place at a time

Thanks a lot for your answer. I've done the same as you said however the game keeps kicking both of us out.

I will test out the feature today (because I had 3 PCs added to my Microsoft account as of yesterday of which I removed 1, so probably because of sync issues) and close this thread if the issue doesn't persist!

Hello, how are you? My name is Mateus. I'm an Independent Advisor and I'll be glad to help you today.

First, welcome to the Xbox community. Only 2 people can play at the same time, however, this only works on Xbox because the console has the function to set it as a home device which would allow you 2 to play at the same time on the Console.

For the sharing to work on the PC, the person who subscribes to the service or who purchased the game would need to log in with the account that has the license in the Microsoft Store on the other pc, and the person who uses that other PC would log their account into the Xbox application in order to start the game.

*Thank you in advance for contacting, I hope this can help you.

I see, but as I said it's probably still going to continue to kick one of you out, account sharing at the same time only works on Xbox due to the function of setting the console as a home device, on PC there is no similar setting, so at the same time will not work

You can already share a game simultaneously on two separate consoles. Set your children's console as your account's Home Xbox and they can access your games. You can always access your games on any console as long as your gamertag is signed into Xbox Live
on that console.