I have three Citi MCs:
- Citi AAdvantage Gold World MC (my main card)
- ClickCiti AAdvantage MC (a fee-free "online only" card they offered several years ago that has a price protection guarantee for online purchases)
- Citi Dividend Rewards MC (for gas/drugstores/groceries only)
I used to have a Citi Platinum Select Student MC that once upon a time gave me great student "zone fares" on AA (alas, they discontinued that program years ago). When I went to open my Dividend account last year, they made me close the Student card because you can only have three personal accounts with Citi at any one time.
Meanwhile, my mother has two Citi AAdvantage Plat World MC cards, because for a while she was exceeding the 100,000 mile a year limit per card.
So you can definitely have more than one Citi card, but you can't have more than three.