Dear Marcel,
For a many-to-many relationship you normally have an intermediate table that is child to both types you want to related. Its explained with graphics here:
http://wp-types.com/faq/how-do-i-associate-one-child-with-several-parents-of-the-same-type/
But in the end, we need to get the data structure first and after we can resolve the problems we find. In your scenario, who do the images belong to? to a review or to a listing? If you really need them to belong to both (ie: you have images attached to listings and you have images attached to reviews) then I would recommend creating 2 separate types for images: ReviewImages and ListingImages.
Can we try to continue this route: What is it that doesnt work when you just have one parent?
Regards,
Caridad