The answer depends upon whether the child support is allocated between the two children in the agreement. If a set amount is allocated for each child, the amount allocated to the younger child will continue even if the amount allocated to the 19-year-old child is not continued. If the agreement simply provides for a lump sum (it is not allocated between the children), the parent paying the child support must continue to pay the existing child support amount. Either parent is entitled to petition to have this result modified when one child reaches age 19.