A secret can be hard to part with. It may not be particularly interesting to anyone else, but you guard it with a ferocity that surprises yourself. I've been seeing someone for more than 3 months and only told my parents just now. At first it was too soon to say anything, then I just didn't and after that it was funny that I hadn't. Even after there pestering me and trying to set me up with good dutch girls. Most people knew already but I never tell my parents these sorts of things. If I had my way I wouldn't introduce girlfriends at all and leave it until I was sure she was the one.