Can I use one Apple ID for 2 iPhones?

Yes you can, but that practice is not recommanded, unless the 2 iPhones are used by the same person.

Shouldn't be this case, the suggestion is to use Family Sharing instead (each person has his own Apple ID).

Regards

Giulio

You can use one Apple ID on all of your Apple devices. But, as ProutGiulio says, you shouldn't use that Apple ID on other people's devices. In other words, don't share your Apple ID with your spouse, your children, your sibling.