gilleshk, I've got to say, I think you're giving some terrible advice. There is no question that the OP is illegally residing in HK, working in HK and/or China without the right to do so, and illegally evading taxation. Saying "oh, don't worry, you'll probably get away with it" is really not helpful, since the consequences of being caught could be so severe.
I would say there's a pretty decent chance of the OP and/or his/her family being pulled up by immigration sooner or later - as has been say, probably more likely the family, particularly if they are doing regular three-monthly runs rather than more natural comings and goings. The immigration people aren't stupid, they do have electronic records, and probably some automated analysis which will flag questionable situations. I think there's probably also a non-zero chance that somebody will notice the lack of taxes being paid - presumably the UK company is reporting that they are paying an employee in Hong Kong, and it wouldn't surprise me if the HK and UK tax/immigration people talk to each other every now and again... And so on and so on.
I think the best advice to the OP has to be to speak to an accountant and/or lawyer who is familiar with tax and immigration issues, as soon as possible - either to normalise the situation, or at least to prepare for when the sh*t hits the fan, be it 1 week or 1 year from now.
The closest thing I've heard to this is someone who lived and worked her for a year, for her UK employer - but who was still paid in the UK and paid taxes in the UK. She lost that job, found a local one, submitted her visa application and was told that she'd been here for a year illegally. After being threatened with fines and even possible jail time by immigration, she did manage to talk her way out of trouble, but it was pretty scary. And she was a) paying tax somewhere, and b) not involving other members of her family...