In Aust what's the definition of PARENT and where do step family fall within the definit. of IMMEDIATE FAMILY?

I'm refering directly to the law concerning Bereavement Leave in the work place and where the law stands concering this. From what I can find the law makes no reference to STEPS in the policy, which basically means to the hard case employer (my employer) that if someone in your "IMMEDIATE FAMILY" dies and they are not Blood Related then stiff bickies. Doesn't matter that they "to you" are your mum/dad, grandparent, brother/sister and have been there the majority or in some cases your entire life, if they are not blood to you or your partner then you are NOT entitled to bereavement leave. I can not beleave that the Australian Federal Government ment this to be the case as it is TOTALLY IMMORAL and paramount to DISCRIMINATION. I'm trying to get some difinitive clarification on this as I was not granted bereavement leave for my my grandads (step) funeral and dread the day that dad (step) dies as I don't want to be told again I'm not entitled. I never knew my real dad or his dad and these two "steps" were all I had in that respect. I feel discriminated against and if the law supports this it should be changed. Can someone help me with this please even FAIRWORK AUSTRALIA are throwing off on this one, they've been useless.