I must have been 3 or 4 when I first experienced Zelda.
Our new neighbours had just moved in, and they had two sons, one of them being a little younger than me. So he invited me over to them, and in that corner in a little room, there was a small TV with a SNES connected to it. He plugged in the game, turned the system and the TV on, and before my very eyes the gates to the magical lands of Hyrule opened up. I really loved playing the game, as well as watching it being played by my friend or his older brother. Being that cool guy with a sword, defeating evil monsters to rescue the princess, it was a great experience for my younger self, and so ALttP didn't only introduce me to Zelda, but to video games in general. I remember being totally excited when I was allowed to borrow the game after I got my own SNES, finally being able to play it by myself.
So, yes, it must have been around age 3 or 4.