Game log In Question

I'm not a techie....I'm just brainstorming trying to help a friend who is designing a game....Is it possible to setup a log in system so that players will be able to only have 1 Account and can't fudge it in some way to get around the 1 account rule ?....Thank You your help is Greatly Appreciated.

Short of verifying drivers licence or some such thing, there is no way to guarantee one person/one account. Is it really that important? I think the purpose behind the rule needs to be examined and mitigated in other ways.

For example, even if we ensure that one person has only one account by providing accounts face to face, what is preventing from me handing my account over to my sister for her use so that she has two accounts?

Most games mitigate this by having terminology in ToS to the effect that any multi-accounting is grounds for permanent ban. They also analyze logins by IP to see if there is a pattern where two accounts can be identified to be driven by same person and promptly issue a warning.

To accommodate multiple people from same family playing, they usually require you to register all accounts that login from same location and mandate that these accounts cannot interact with each other in game.