Copyright ownership is a lucrative business. Some families have had success reclaiming ownership while others have not. In the latest permutation, the family of the composer of Santa Claus is Coming to Town was not successful in reclaiming the composer's copyright. Unfortunately (or perhaps fortunately) , it's debatable whether the decision can be attributed to a contract issue or the reversion clause of the Copyright Act.
Legal information and research resources from The Ohio State University's Michael E. Moritz Law Library