Bob Anderstein is a character heard on the Oscar Zulu frequency originating at the radio station of the same name.
Background
At the time of the transmission, his son was dying and he was using a radio frequency to call for a doctor to come to his family's sewer hideout. The player can pick up the frequency and discover the sewer only to find the whole family is long gone. It is likely they put the signal on the air just after the bombs fell. You can see the parents' skeletons on the floor... but not the boy.
Appearances
Bob Anderstein is only heard in Fallout 3.
Trivia
It is also speculated since the child skeleton is not found, that the sick child is your father. It is not confirmed, though.