Supplying information about yourself, such as Marital status, Age and how many children you have is completely optional.
In fact, we don't expect that you'll fill in any of those details, but we thought that we'd ask, just in case.
The information helps us know who visits our site, and what they use it for. We are constantly refining the site to better serve our audience, but of course it helps if we know who you all are. 
Don't worry about your privacy being abused though. We take your privacy as seriously as you do, maybe more so. Read our Privacy Statement for details.
The bottom line is this: give as little or as much as you feel comfortable with. Thanks.