Complex sentence: In addition, where there is joint custody, the child is considered to have two custodial parents and no non-custodial parents, thus a custodial parent (obligor) will be required to pay the other custodial parent (obligee).
Split into simpler sentences: In addition, where there is joint custody, both parents are "custodial parents" and neither parent is a non-custodial parents, or in other words the child has two custodial parents. Thus, with joint custody, one custodial parent (as an obligor) will be required to pay the other custodial parent (as an obligee).