There are several factors that determine whether you are in a defacto relationship. Firstly the relationship must be of an intimate kind and not just close friends. The courts can declare a defacto relationship if you have been living together for two years or made contributions to property or you have a child together. It will be very difficult to establish a defacto relationship is you have not predominantly maintained the same residence.
Same sex couples are not treated the same way as heterosexual couples. Defacto law in relation to property settlements works the same way as married couples.
There was a recent case in family law with a same sex female couple together for 27 years. Even thought they were in a close domestic relationship and considered a defacto couple they never shared finances and kept all the property and debts separate. Even though the court found that they were a defacto couple the court refused to make an order for any division of property given that they had never mixed finances and always owned separate property and bank accounts.
In relation to children, it makes no difference whether you’re married, defacto or you’ve never lived together. Being a biological parent is enough to seek children’s orders from the court in relation to spending time with your children. There is also legislation that allows anybody who has a close personal connection with children to apply to the court for parenting orders. The courts must always act in the best interests of the children regardless of who is applying for an order. In this regard, Australian Law is quite progressive in comparison to other countries in the world. In places like the UK and in some states of the USA the mother automatically gets sole parental responsibility if the parents are not married.