how can two family members with own profiles sign in at the same time with a multiplayer game

Make sure that only one profile is signed in on each profile.

Yes you can be signed into 2 profiles at the same time. Each profile will be signed into it's own controller.

Some games allow you to play online multiplayer via split screen.

Each of your kids would need to have their own profile (linked to separate email addresses) if they want to earn their own achievements, etc. They do not need to know their passwords, you can set the console up to remember the passwords when they sign in
if you like.

You can set the console to only log in one profile at a time. Any other profile would need to be logged in as each person plays.

On the Xbox One, you can share one Gold membership among all the family. Head to Settings and scroll right until you see Add to Family. You can add each family member there to set up sharing. If the game supports split screen multiplayer then both kids
can play at the same time. Examples of games that support split screen are Minecraft and Disney Infinity 2.0.

Here's how it works:

1 - You buy a game & it links to your account; this makes you the primary owner.

2 - Any other profile on your console can play your game as long as your profile is on that console.

3 - How family members are chosen exactly is currently unclear.

4 - Family members can play your games on other consoles, but only 1 family member at a time.

5 - At any given time, you (as the primary owner) & ONLY 1 other family member can play the same game at the same time on separate consoles.

6 - However, you can have more family members on your console playing with you as well (so you could potentially have you & 3 other family members on 1 console (split-screen) & 1 other family member on another console for a total of 5 family members playing
the same game simultaneously).

7 - It is unclear as to whether multiple family members will be able to play on the secondary console at the same time as the primary console.

Hi Randy

each if my two kids have their own accounts as family members already set up. What they want to do is use the online gaming features of xbox live under their own profiles on their own consoles. If they are part of my microsoft family group and i set my personal
console as the hime console do they share ALL gamepass ultimate features (inclusive of live features) on their own profiles in their own consoles?

if not how can this be achieved?’

thanks