This is an evolving area of law that needs NOT be dismissed so lightly.
The law presumes that once a child has reached the age of majority the child is then capable of self-support. Seegenerally 59 Am. Jur. 2d Parent and Child 89 (1987); 67A C.J.S. Parent and Child 62 (1978). The situation may arise, however, where the child is disabled, mentally or physically, and therefore unable to support himself/herself upon reaching the age of majority. Most states have adopted the rule that parents have a common-law duty to support their adult disabled children.
The legal citation for Pennsylvania that you need to study is Commonwealth ex rel. Welsh v. Welsh, 222 Pa. Super. 585, 296 A.2d 891 (1972);
Pennsylvania has also focused on the economic aspect of disability. In Hanson v. Hanson, 425 Pa. Super. 508, 625 A.2d 1212 (1993), the court stated that to determine whether an order of support is appropriate, the test is whether the child is physically and mentally able to engage in profitable employment and whether employment is available to that child at a supporting wage.
Thus, the adult child who, because of her handicaps, only earned $2,850 as a laundry worker was disabled and entitled to support pursuant to the guidelines. See also Sudduth v. Scott, 394 So. 2d 536 (Fla. Dist. Ct. App. 1981) (mother had duty to support adult disabled son who was blind and retarded and incapable of holding a job); Commonwealth ex rel. Cann v. Cann, 274 Pa. Super. 274, 418 A.2d 403 (1980) (adult child who suffered learning disability and was unable to earn supporting wage because of mental capacity, even though she worked 40 hours per week at a cleaning job and babysitting, was entitled to continued support); Commonwealth ex rel. Magaziner v. Magaziner, ___ Pa. Super. ___, 419 A.2d 149 (1980) (parents' duty to support child did not end at majority where the child required psychiatric care and was unemployable).
Timing is also critical. As in your case, the disability must present itself during the minority of the child. Once the child reaches the age of majority, the disability cannot be used to revive support. See Sacred Heart Medical Center v. Williams, 637 F. Supp. 184 (E.D. Pa. 1986) (applying Pennsylvania law);
In this instance, the support order is in place. However, because the child has reached the age of majority, is receiving state aid and has a managable disability, it will be incumbant upon the party wishing to continue support to prove that the duty continues to exist.
"Because the duty to support a child ordinarily terminates when the child reaches the age of majority, it is up to the party asserting that the burden should not terminate to show that the adult child is in such a feeble and dependent condition physically or mentally as to be incapable of supporting himself/herself. Moreover, the burden is generally not just a preponderance of the evidence, but is clear and convincing evidence. E.g., Free v. Free, 581 N.E.2d 996 (Ind. Ct. App. 1991); Speight v. Speight, 933 S.W.2d 879 (Mo. Ct. App. 1996). "
Therefore, I would advise you to file to cease support payments citing the age of majority and disability payments as income to the child. If the ex wants support to continue, she will have to refute your assertions and carry the burden of proof.