Obviously the grandparents would want to have themselves covered lest their unstable daughter showed up and wanted to take Barry back with her to whatever her next stop in the jungle was going to be.
Clearly an adoption for the purpose of protecting the grandparents and Barry would screw up the works regarding birth certificates and such.
It's not even all that uncommon today, when there are more opportunites but less incentive per opportunity.
Two of my wife's coworker's (both PhD's) adopted their grandson for example.