https://support.chess.com/customer/portal/articles/1444776-can-i-have-multiple-accounts-
Is Chess.com Rating Meaningless?
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Yeah, I get it, I'm just saying it's a silly rule because it's unenforceable (multiple people may have accounts using the same IP, so it's impossible to prove a violation has occurred) and it's pointless (you don't need Chess.com to analyze games in the first place, you can use another platform).
I may have several accounts, but good luck proving which are mine and which are my spouse's, or brother's, or father's etc.
You will each need to use a separate email address to join. Once you are all set up, you cannot play any rated games against each other on the same computer and you each must log out after playing and make sure you aren't playing on one another's account.
To avoid confusion, it's a good idea to write at support and let them know the usernames of everyone so that they can have a heads up in case you are suspected of having multiple accounts.
Moreover, multiple people may have accounts using the same IP, so how could they possibly prove one person has more than one account? What a silly rule altogether.