So they don't have to pay the marriage penalty. They can each file as single with the one making the higher income itemizing deductions and claiming the children as dependents (or two of them if it is Loving); the other one can take the standard deduction and one of the dependents. One of them can even claim as single head of household. By the time they are through, one of them might be getting EIC money back. Bottom line is they will have a much lower tax liability than they would if they were married.
Good points - whether taxes, or losing an alimony stream, or avoiding potential child support payments on the oldest child, there is most likely a good monetary motive involved here for ol' Fondray.