Stacking item and subitem data

Hey, I am trying to stack data from a main item and a subitem in a bar chart.
From previous posts ive seen it looks like this is not possible however i wonder if there is a work around.

I want to take the person who is assigned the item (currently in main item) and copy this down into the subitem. Firstly for the whole board so i have the initial data for my chart and then moving forward so it works long term.

My Y axis will be a count and the x axis by person stacked with a count of how many of a certain type of thing they are doing.

Hope that makes sense and any help truly welcome!