Using members in channel custom field

I’m making the rating system now. I have created a channel called “recipe-reviews” and have put a custom field in there as a relationship to the “recipes” channel, so when publishing a recipe review, you can select the recipe that the review belongs to. That’s good. I want to do the same thing for members, so we can post reviews on a member, there doesn’t appear to be a members relationship in the channel custom fields administration - is there some way I can do this? Is there a way to plug-in a custom relationship to the custom fields administration or something, any way that I am able to do this so that when I publish a member review I can select which member the review belongs to? I already understand that there is an author select in the options tab, but that is for the author of the review, not for the member who the review is about.