Someone help me

I made a Facebook that’s like undercover (my family won’t know it’s me) Bc my parents don’t want me on there and I’m worried my older siblings might find me on there and I was wondering when I post to everyone does that mean that ppl would know it’s me or no? I have a fake name and a pic of a crown but I’m scared of my family finding out it’s me. Could I block them from finding me?