I have only told some family members but I am a bit of a shy person thus don't feel comfortable letting my family know because I just don't need any criticism from them personally that could potentially lead to silly arguments. Also my kind of content is not something most of my family is interested in. But that's just my opinion. I don't have any interest in them subscribing if they are not interested in my content.
lol I didn't tell my family until about three years in. I let them figure it out on their own. YouTube is great about showing your stuff out if you do it right, I was more focused on that than trying to gain a handful of views from family. By the time they saw my work I had an entire channel with multiple playlists and 150 videos for them to enjoy watching.
I didn't really tell anyone honestly, my close friends eventually caught on but as far as family goes, only my parents know. I don't really tell anyone about it unless I genuinely find it to be relevant for them.
Some people know that work with me, and a scant few family members. But not a lot. I don't promote it locally, and really don't want to. I have a decent number of subs and am monetized. I don't *need* them to know. It wouldn't benefit me in any way, really. Plus it'd be totally irrelevant to their interests anyway.
But if a comment about Youtube is made, I'm the first to chime in!