Back in March, Microsoft announced that Xbox Live Gold Family Packs were being phased out. Now, individuals currently on the Family Pack are now being swapped to individual accounts starting August 27th.
Each individual account will have the remaining time left on gold that was on the Family Pack plus three extra months for the inconvenience of being swapped out of the program.
This means that the Family Pack features, which included account monitoring for the parent account, will no longer be available. However, Microsoft states that parental controls will still be available.
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This article seems to confirm that it will work on 360, http://www.slashgear.com/xbox-one-will-allow-multiple-users-on-single-xbox-live-membership-22283155/. That makes sense, if you can go cross platform with the membership, the accounts should work too!