Help and advise my son has shared information shared with another gamer

First thing to do is try and log into the account at account.microsoft.com and change the password if you can. If you're able to do this you can check from there if any purchases were made on the account.

If you're unable to log into the account then you will have to attempt to recover it. To recover an account that has been compromised or hacked, see How to recover a hacked or compromised Microsoft account - Microsoft Support.

The account recovery form is located here Help with the Microsoft account recovery form - Microsoft Support

So my old Xbox one has gold live but it’s not linked to any profile. My son uses it and we gamer share but i can’t use the gold live

It’s the Ultimate version

I should say that my son has his own account/Xbox gamer tag.

I’m sharing the Ultimate pass with him as a family member.

As already mentioned, the only way that a message could be sent without knowledge is if the other gamer had access to the account. The sharing of account information is against the code of conduct. It is also not a defense to say "I didn't send it" as the
account holder (your son) is responsible for all actions carried out by his account.

If he has shared his login information, I would suggest checking all account information, email and contact details are correct at https://account.microsoft.com and changing passwords
etc.

Hi there

I am not entirely sure if you can games share with 3 consoles. However i can offer an alternative solution.

What if your son and daughter games share? That way they can share the games and gold. And then you can enjoy your games and gold that way the kids are sorted.

Hopefully another fellow gamer can offer some suggestions for you.