Does 你家孩子真多 follow the topic-comment pattern?
It’s a topic-comment structure, but exactly what the topic is is open to interpretation.

It might be “你家”.  In that case a rough English version would be:


  Your home – how many children there are here!


Or it could be “你家孩子” meaning:


  The children in your home – there are so many of them!


Which one to choose depends on context.  If you heard this spoken, there might be intonational clues, e.g. a pause after the topic.