Combining iCloud data with High Sierra

My wife and I have iCloud accounts and family sharing and High Sierra.

We'd like to combine our data and expand our space with one drive instead of two.

Right now I see different iCloud drives on both of our iMacs, but Googling, and looking at my iCloud settings is not indicating to me how to change whose account has our drives. This should be possible with High Sierra, but I'm not figuring it out.