'What you don't know can't hurt you' is, as it turns out, utter tripe. The new big thing in the self-help world, Systemic and Family Constellations, is showing us that family secrets are profoundly damaging, not just for the poor gay uncle that had to end his days alone in Morocco, or the shunned Edwardian single mother or the bi-polar aunt locked up in an asylum, but for the three or four future generations who unconsciously seek to bring the excluded family member back into