My nephew is 5. Im 33F.
A few months ago he asked me “Auntie Franny, are you a grown-up?” I got really quiet, cautiously looked around, put my finger to my mouth and told him
“Im still a kid, but you can’t tell anyone because no one knows.
“His eyes got huge and he loudly whispered “I KNEW IT!!!
“Now every time I see him, he comes up to me at some point and whispers “don’t worry, I haven’t told them.”
Then proceeds to ask more question about my life as a secret kid. And every time I’m video chatting with him and my sister, he sneaks an obvious wink, and I wink back, and only we know what that wink means.
And to this day, he is the only person that knows I’m still a kid and that I’ve been faking it all this time.