[quickthrowman]

Disposable income is Gross Income minus Taxes. A 2 parent family with 2 kids making the same as a DINK couple would have a lower tax burden and more disposable income, but the DINK couple almost certainly has more discretionary income, which money left after paying for necessities like housing, food, and medical care.

[BobaFloutist]

On the other hand, a 2 parent family with 2 kids is quite likely to not be making the same as a DINK couple.