My kid's profile (Family account) can't connect to xbox live and age restricted when...

to play that game requires a 2k account which is created when you start the game, i think the minimum age is 13 or 16 cant remember but if they are to young then they cannot play it.

In order to monitor your kids, you should add their accounts to your parent account in the Microsoft Family settings.

Go to
https://account.microsoft.com/familyand sign in with your parent account. There add the two accounts of your kids (make sure that when you create the accounts for your kids, that you enter their proper birthdate, as this determines when the account becomes
an adult account, that can't be restricted).

There you get an overwiew of what the kids did and also set restrictions, like playing time limits per day or week, or restrict games to a certain age, (dis-)allow them to talk to internet strangers via Xbox Live etc.

If you want to use the Xbox App, be aware that this is not a monitoring tool. The Xbox App is just a "social network" for gamers. You can add your kid's gamertag names as "Friends", and you can see what they are currently playing. If you look at your friend
list, you would for example see "Kid1Gamertag is playing Minecraft" under their name. But you will not actually see their game screen.

Wouldn't really work due to the amount of kids who lie about their age when starting an account so they can download age restricted content etc.

Plus there just as many idiots that are my age on live as there are youngsters.

I've turned all my sons restrictions off and he still can't play online. We have had so many issues with the account restrictions, I guess it's time to create fake profiles with over 18 ages just so my kids can play Minecraft...

This usually means you're account is underage or has restrictions. When you created the account did you use your real age? Because while you're able to change your age after the fact it won't be recognized as your official new age. This is to prevent kids
from just changing their ages to bypass things. You may need a parent or guardian to add you into a family account and adjust the restrictions for you.