This just has to be where 'daddyo' comes from.
another correct solution is "a daideo"
That would be “her granddads”.
On the audio, how are you supposed to tell if it is 'her grandfathers' or 'his grandfathers' given that the 's' is already pronounced as 'sh'?
On the "his grandfather" the "s" would not be pronounced because it would be silent. The word would start with the "h" sound.