Dear Mr. Das,
Request you all to note that until and unless we go through the CVs, complete the screening process we may not be calling the candidates for interview.
The reason behind asking this question basically is that even though the candidatee experienced but the candidate is sitting infront of new people and for any body and every body it needs some time to adjust and come to normalcy hence the very easy thing and useful thing is knowing each other. The interviewer expects more on your family as they know about the qualifications, places he worked and the age etc.
By asking this question they expect that the candidate will be explaning more about his family and some about himself, that means the candidate will be taking a good time which can be utilized for assessing his body language, confidance levels, speech / communication, logical thinking, the corelation between thinking and expression, sequences etc., etc.,
In my opinion this will reduce the stress / curiosity, brings a cordial and friendly atmosphere in to the interview chamber.
If you are a real asseser you should start your assesing right from how the candidate knocked the door, how he wished, has he waited till the team offering the chair / sat on his own taking an initiative / the posture he sat, if he is unable to understand / hear the question how he is requesting for getting the info once again etc., need to be obsedrved.
Interviewing is an art and I don't find any wrong in asking some different type of questions, but there should be a reason behind it and finally it depends on you how you / in turn organization will get benefit out of the same by choosing a right fit.
Regards - kameswarao