How do you answer this?

A few weeks back we took my 3 year old daughter swimming with her male cousin. She looks up to him and when he took his shirt off to swim she wanted to do the same. At that point my wife and I started having talks with her about modesty and not letting boys see your bathing suit parts. We talked about how boys and girls use seperate bathrooms and how it's ok to change in front of girls but not boys. We told her one day when her little brother Jonny gets older they'll change separately. She was ok with the whole thing and never brought it up again. 

Fast forward to last week. I'm getting out of the shower and forgot to lock the door. She comes busting in as I'm reaching for a towel. I thought I was in the clear but then she asks me, "what was that daddy?"

"Nevermind", I said. "Hurry up and get out of here so daddy can dry off". 

You could see the wheels turning as she stood there in silence looking at my towel. I was nervous wondering what she'd ask next. 

"Daddy, since you're a boy and Jonny is a boy does that mean he can see your big huge weiner?"

"Go ask your mother" was all I could think to reply.