Can't play 360 games on xbox one using kids profile

He dosent have a xbox live account its family share so there's only one subscription

Now I'm a bit confused.

What exactly do you mean by "kid profile thing on your account" then?

Do you have an adult Microsoft Account, and is the kid added to
https://account.microsoft.com/family with their own child/kid account, or what do you mean exactly with the "kid profile thing"?

Ideally, each family member has their own Microsoft Account and Gamertag, so each person can save their own gaming progress and doesn't unlock achievements for someone else.

The family sharing is done on the Xbox One console. One person that owns a Gold membership can share that membership to one "Home Console", and everyone playing on that console can benefit from the Gold membership and the games that person purchased.

The Xbox 360 does not have the concept of the Home Console sharing. So if your kid is supposed to play online Multiplayer on the Xbox 360 (a real Xbox 360 console, not an emulated Xbox 360 game via Xbox One backwards compatibility), each account playing
on a Xbox 360 would need a separate Gold membership.

Ya its family share and ya its an xbox one I keep getting 80150016 error message looked it up did the things it said still getting it and thanks for the help its awesome that people take the time to help

Has he been able to play Xbox One games with his account?

If so, he has to download his account on the Xbox 360 by pressing the Guide button, signing out other players with X, and then choosing "Download Profile".

If that was already done, what is the exact error message you or the cousin gets?

It pops up asking him to sign into a xbox 360vlive account but he dosent have one how can I get the account he plays xbox one to play 360 game's

Is it possible that the account that gets the error message during sign in has a very long password (longer than 15 characters), or that the account is protected by Two Step Verification (you can check that at

https://account.live.com/Proofs/Manage)

If so, go to the linked page, and have the page create an app password, then use that app password instead of your regular password when you sign in on the Xbox 360.

Another question: Is the cousin already playing (offline) on the Xbox 360? Do you mean that when you say "kid profile"?

If the kid has their own offline profile on the console, have them sign in on that offline profile, then press Guide button, and have them "Join Xbox Live".

If the kid has never played on a Xbox with their own account, they might need to have a Gamertag by going to
https://www.xbox.com and signing in with their own Microsoft Account.