Google Merchant Center product reviews

[LesleyPaone]

My googlefu is not good enough to put the words together to find an answer for this, but I am sure there is one out there.

I am making a review feed for a client's site to submit their product reviews to google merchant center. But one problem we are having is that the reviews are generalized, like how amazon does it.

A sample product would be Whey Protein, this product is available in 4 different sizes and has 4 different GTIN's (one for each size). But the reviews we collect are just for the base product of Whey Protein.

What I am trying to figure out, is if I can assign a parent GTIN, then correlate the reviews to that GTIN and then let them populate for the child GTIN's some how.