I don't know if gbc is guilty. IMO the strangest behaviour was from the very beginning when abc went "missing".
Why wouldn't he call the local hospitals first? Or check with police that there had been no accidents or pedestrians hit by vehicle etc?
Why go straight to reporting a missing person...
I am sure these people love their grandchildren regardless of what their son may or may not be guilty of.
It would be heartbreaking for anyone to watch their grandchildren sob and farewell their mother