The DNA-ID podcast covered this case yesterday and did a good job of it.
Doe ID 'The Boy In The Box' Joseph Augustus Zarelli
According to the hostess of the podcast, all of the surviving relatives of both biological parents claimed no knowledge of JAZ, and were quite surprised to find out about him; and both families are certain that the boy did not live with either biological parent. Although, the woman who sold the hat that was found with the boy did say that Gus Zarelli resembled the man who came in and bought the hat (the customer requested that she custom-make a strap for the hat, so she remembered the transaction). If the boy was kept by the Zarelli family he might have been kept hidden away in a basement or attic. But from the information thus far released, it's hard to claim anything for certain.