Is it just a toddler thing?
For example, he has a Teenage Mutant Ninja Turtles plate, and he reliably calls the turtles mummy, daddy, DS-name and DD-name (always same turtle = same person). This was turtley totally instigated by him.
If we're reading a book and you point to a person, he'll usually say it's one of us. In the book "Orange Pear Apple Bear" the bear on each page is a different person, now extended to include Nana and Grandad. Until recently they were all just Bear.
Is it just DS, or do all children do this? (familiar faces must be people I know??)