How to track down an owner of abandoned house?

[Scott Peace]

Hey all, thanks in advance.  We have a house that we know is vacated and in a prime area.  The city posted a memo on the door about high grass to the owner, so we know the owner's name.  We have already looked it up on the PVA website and it appears to be an older couple that passed the house on to their son, but that is far as we have gotten.  We can't find anymore information about the son.  Any suggestions on how to proceed from here?  Thanks.