A lot of general information about a person is free on the internet. Information such as their middle name, cities that they live or lived in, their relatives' names, age and etc are all available to the public (anyone) for free. It is not illegal to obtain these information and you can pay the website a fee to view more detailed information about the particular person that you are interested in.
Go to www.ussearch.com. They allow you to put in the first, last name and middle initials. It is better to put the state of their residence and approximate age. For a name that is popular, it is important to put as much information as possible to narrow down the search. Now, all you have to do is hit search and all relevant people's information will come up.
If you know where the person lives and their approximate age, it should be easy to spot the one on the results page. You will be able to find out their full middle name, their real age, and the relatives' name. Now you have fulfilled your curiosity and found out information about the person that you are interested in.