How should you reply when asked you grown up?

I think you meant to ask about when you are asked IF you are grown up? Usually such questions are asked by older aunts or uncles or people one does not really know. The questioner is actually making "small talk" or, perhaps, just wants to make you uncomfortable. If you believe you ARE grown up, answer with a smile on your face and a lighthearted laugh. Say, perhaps, that since you are not yet all grown up (the older adults will like this) you do not yet know. Ask the questioner what he or she believes. No matter what s/he says, do be kind.