If there is anything I should keep a secret or low key it should be my financial life. I don't let people know about my bitcoin life. Nobody even my family members don't know am a bitcoiner.
Not all family members are good people. We cannot know what they will do if they know you own bitcoins at home. It is one of reason but another reason is you will avoid pressure to buy or invest on behalf of your family members. Many of them will not be ready to learn and just want to send money to you and ask you to buy and hold bitcoin for them.
What will you do if in buying process, you make a mistake (address typo) and lose money or you fall into a trade with a scam trade partner? What will you do if you lose your wallet in holding process by a hack, laptop steal ...?
Will they be ready to accept such personal mistakes or accidents of you and let their money go easily?