reberr, you're story makes me think of my BIL's niece. When she was born her mum stayed home to take care of her, then after a year it was her dad's turn. But she (at around one year old) figured that "Dad" was the one who went to work whereas "mum" stayed home. Her dad was not pleased when she started calling him mum. But then when the mother came home she got the roles right.
But I must say, it was very logical of her, at one nonetheless. I haven't seen her since this summer, when she was two, but she's really bright and well-behaved, it's so much fun playing with her, because if you try to teach her something she really will listen and learn. (Plus I love the fact that I see her just a couple of times a year and she's not shy or anything)