Game sharing???

I feel like I probably already know the answer to this question but I just wanted to make sure. SO! I'm already game sharing with my partner. My account is set to primary on his Playstation. His brother recently bought a PS5 and my partner is wondering if he can game share with his brother by setting his account as primary on his brother's Playstation? Probably sounds dumb and the answer is probably obvious but he just wanted to make sure if it's possible or not!! :)