To be smiling cos the shine has slipped?

5 year old twins stayed over the weekend and their GD is their number 1, with me in the shadow, I do everything to please them, arrange everything we go to, am kind and lovely to them, but still GD who is the 3rd kid and means I have to control all three of them is just the best, the hero! BUT, a question was asked this weekend (and I keep mentioning it to GD whilst laughing hysterically), the question asked by both of them was "GRANDAD, WHY ARE YOU SO GRUMPY", hehehehehehehehe.