"Is it necessary to give your personal information, such as your address or details about your family to others?" No, because that's like telling your credit card number and PIN to a stranger you've never met.

At times you may be asked to provide personal data at well-known corporate websites. Your personal information should be kept safe, including expired credits cards. You might need to give your personal information for age verification to register for some online services. Make sure you first read the privacy agreement and understand whether the website will forward the data to any third parties. At the end of the day, you don't want to be fooled by an Internet con artist.
http://www.pco.org.hk