they asked you this question might due to company policy, some company not allowed close relative work in the same company. 2nd is they want to know anybody recommended you to the company and last i will say they just asking.

Techinal question i will say is important if your job need technical knowledge. Yes if you do not know to answer better say do not know cause if you lie people will know then say tata to your job. about technical knowledge you have to do your homework cause job related or requirement you should able to answer. i will say if you do not know less chance already to get the job.