Microsoft's Xbox LIVE Gold Family Pack offers four Xbox LIVE Gold accounts for $100. Can I take two separate Xbox LIVE Gold accounts and make them both part of the same Xbox LIVE Gold Family Pack account? Microsoft has already said that a single account can be migrated into an Xbox Live Gold Family Pack account.
According to Microsoft, Yes.
To do so, you need to add the secondary accounts to the same console as the primary account holder. You then "activate" them into the Family Pack. After that, you can recover those accounts onto different consoles, and etc.