Hi, not sure if you saw my initial query above - were there other candidates being interviewed for the position?
Yes but I dont think they were interviewed
It is not illegal to interview your own son or any other relative or friend for a job in the same company. However, this could go against company rules where the employer wants to act in a fair and independent manner so there could have been a company policy dealing with this and it is worth checking if that is the case.
Generally though, a person could be employed in a job for whatever reason they want, even if they are related or friends with someone who makes the decisions and they were preferred over other candidates because of these ties. The law does not allow preference for discriminatory reasons, for example if other candidates were not selected for the job due to their age, gender, race, religion, etc that would be unlawful, but if the sole reason for preferring one person over another is because they are related to you or your friend, then that is entirely legal and possible.
Hope this clarifies your position? If you could please let me know that would be great, thank you