Hello. My family wants to see the games I'm making, but I don't want to show them my main account for privacy reasons. Would it be against the rules to create another account to show them the same games? I understand if not. Thanks in advance. 

Not sure, but I think you might have to prove ownership of the games if itch.io staff discovers it. Otherwise it should be fine if you don't use multiple accounts for cross-promotion or to deceive people.

I believe it is allowed, I seem to remember doing that in the past.

Make sure both accounts don’t interract with each other in any way, and you should be fine.