2 xbox one same account

From the account you want to enable Kinect sign in. On the dashboard, navigate to settings. From Settings, click on "Sign-in, security & passkey." Then click over to the right once with your joystick so your under the sign-in & security tab and click on
"Kinect sign-in." If you do this with each account, once that player walks in front of the Kinect. It will automatically sign them in.

If they're only using one console, the account with Gold should set the console as their Home console. This will allow both kids to play online without having to purchase a 2nd subscription. https://beta.support.xbox.com/help/hardware-network/console/my-home-xbox

So you can have multiple accounts on an xbox 360 or xbox one and they can be on both at the same time but you can only log into one of them at the same time. Now to recover both onto a new console you will need to seperately recover each account. Each one
will have a different email and password, and if a gamer tag shows up that is different to the one on the xbox 360 that means that you may have entered the wrong email and you'll need to just double check that on the old console as the emails will be stored
there.

No, you will need two Gold subscriptions. The sharing feature is for one console sharing the gold to other profiles on the console.

Listen to all the folks telling you how to do it without buying a second live membership.