I have previously written about paying child support even after you have discovered a child is not your biological child. In a similar vein, a recent decision in New York held a non-biological parent from a homosexual couple liable for child support. The court found that is was compelling that the non-biological parent undertook to care for, and raise the child, therefore was responsible for child support.
This brings me to a broader point...in family law, the decisions that you make while the family is together has HUGE impact on what may happen in court. Your past actions are what the judges use to make decisions.