Wearing diapers around your family or even parents without them knowing about the diapers you're wearing is pretty easy.
When wearing a diaper around family or parents just put the diaper on as normal and then put a pair of underwear or boxer shorts over the diaper.
The underwear or boxer shorts will help to cover up the diaper to make it nearly invisible and if your shirt rides up then they will just see the boxers or underwear and not the diaper.
That works for hiding your diapers in public as well.
Then just put a pair of pants or shorts on over the underwear and diaper and then nobody should notice.
I used to put underwear over my diapers before going in public or around family but now I wear just the diaper under my pants or shorts and nobody notices the diaper.
Most people are too busy with their own lives to be staring at your bottom and they are not really looking to see if you wear a diaper.