While a small amount of whale hunting does exist, it's a fraction of what it once was.
The problem with "repopulating" Earth's oceans with George and Gracies offspring would be the size of the gene pool. Also,we have orcas in the waters here and they don't breed between brothers and sisters (don't know if that applies to humpbacks). These are intelligent creatures and not brainless animals, if humpbacks also shy away from incest any whales resulting from George and Gracie die out after that first generation.
Would a future Earth force
sapient beings to produce children?
Legally and ethically?