Can a parent be required to provide child support for an adult child?

Yes, if two conditions are met. 1) The child must be disable and unable to provide for his or her self. 2) The disability was known at the time the child was a minor.

Tex. Fam. Code § 154.302 (a) The court may order either or both parents to provide for the support of a child for an indefinite period and may determine the rights and duties of the parents if the court finds that:(1) the child, whether institutionalized or not, requires substantial care and personal supervision because of a mental or physical disability and will not be capable of self-support; and(2) the disability exists, or the cause of the disability is known to exist, on or before the 18th birthday of the child.