Multiplayer on State of Decay 2 Cross Platform

Okay. So i have an Xbox with my main account having bought all the games. Then I bought a gaming Laptop, and used the same microsoft account to buy state of decay on PC, it synced it to my xbox and whatever. I have a younger brother that i would like to
play the game with, how is this possible? He has an account on the Xbox, and his account now has the Live subscription. Last time we tried to play it kept signing me off the computer because he had to sign into the main account for the games to work.

:)