microsoft store xbox and pc sharing games

You can switch accounts through the Microsoft Store or through the Xbox app. However, games cannot be shared on the PC.

yes, in the xbox application for pc, below the game title the legend "windows 10" appears, also in the microsoft store, a legend "game pass: Windos pc" appears

The account of your mother will need to be signed in the Microsoft store app while your account will be logged on the Xbox app, this will allow you to share the DLC and any other game pass feature on PC. That's the only way to share her account's DLCs with your account on PC.

No. Game sharing doesn't work with PC games. Your son would need to be signed into his PC with YOUR Microsoft Account to install the game from the Windows Store.

On PC the sharing of games works differently than on the console.

On PC, your Microsoft Account needs to be a member of the Microsoft Family together with the account owning the games. You can add each other to the Microsoft Family at
https://account.microsoft.com/family

After that, sign in on the Windows 10 PC with your own Microsoft Account. Then have the person owning the games come over, and open the Windows 10 Store. Sign out of your account from the Windows 10 store, and have the person owning the games sign in on
the store.

Then have them download the game(s) they own and want to share to your PC.

After the games have been downloaded, the person signs out of the store, and you sign back in.