Translation:Father and also mother are in the city.
It might be a mistake. As far as I know, 'quoque' follows the word it refers to. So it would be more like "Father also and mother are in the city". It would point to 'pater' and not 'mater'. If it's some kind of exception, I guess someone with more experience with Latin could explain the logic behind the structure.
As far as I know, 'quoque' is an adverb and thus not declinable.
But I also wonder how to recognise that 'quoque' should refer to 'mother' in this sentence.