Maintaining information of a relationship of target volumes comprising logical copies of a source volume

Provided are a method, system, and article of manufacture for maintaining information of a relationship of target volumes comprising logical copies of a source volume. Information is maintained on a source volume having a plurality of data units and a plurality of target volumes created at different points-in-time maintaining a logical copy of the data units in the source volume for the different points-in-time. A source downstream pointer is generated for each data unit in the source volume to point to a corresponding data unit in a first target volume. For each target volume data unit whose data is maintained in the source volume or another one of the target volumes, a first upstream pointer is generated indicating one of the source and target volumes from which the target volume data unit inherits data. For each target volume data unit whose data is maintained in the source volume or another one of the target volumes, generating a second upstream pointer indicating one of the source and target volumes having the data for the data unit.