Well said, Mr. B.

In fact, Kay did lose custody--we saw that near the end of GFII, when Connie was rushing her out of her visitation with the kids, and she ran into the Dreaded Corleone Stare. The divorce may already have been final by that time--Nevada was one of only two states that granted quickie divorces at that time (Idaho was the other). Divorce courts then and now routinely grant custody to the mother, except if the mother can be proven to be mentally, physically or morally "deficient." Kay's divorce would have been grounds for "moral deficiency" in those days, and given Michael's money, influence and fear factor, a judge would have readily granted him custody.