How to unpublish a node and any related nodes?
Yes this seems perfectly possible with Rules ... In your case, the crucial part of such rule is a Rules Action to perform a Loop. If you're not familiar with such loops, then I strongly recommend to have a look at the tutorial titled "Lists and loops".

In your case, you should use (at least) have a Rules Action to create a loop related to your 'related "Review" nodes' (as in your question). After you do, you should iterate over each item in that list. And for each iteration you should then perform a Rules Action to "unpublish the review being processed in the loop".

Done

PS 1: Refer to my answer to "How to set multiple values to an unlimited Term Refence field with Rules" for some sample rules that are like a variation of your question here.

PS 2: I assume this is about D7 ...