I'm sure you're right about the "reference to the main character in question" idea - and yes, there are quite a few examples from children's literature (the Katy books also spring to mind, the first sequel being just a couple of years after Through the Looking-Glass).

I have to admit that Pamela is a guilty pleasure of mine, but the sequel (in which Mr B goes off the rails and Pamela throws herself into educating her daughter on Lockean lines) lacks the power of the original. As sequels to Pamela go, Joseph Andrews is better.