Here is where I think the laws should fix things. Once you hand over your DNA, you no longer have any rights in the ordinary biological sense. Sperm and/or egg donors should NEVER be hounded for child-support or any such nonsense. This is a similar (albiet different) situation. You put your semen in a cup to be used (in certain contractual ways) in a fertility clinic, you should have ZERO biological rights or responsibilities. ALL rights and responsibilities should be contractually defined. The father should NOT be the person whose DNA matches, but should be the person stated in the contracts to be the father. Ditto for the mom.
I don't think the bio-parents deserve ANY legal standing based on biology. The contract, and NOTHING ELSE, should be legally binding.
No matter what any clinic tells you, courts will still be liable for child support. Every form should have stamped on it, "NO MATTER WHAT, YOU MAY BE RESPONSIBLE TO PAY CHILD SUPPORT FOR ANY NUMBER OF CHILDREN."