I wouldn't say the taste of kidneys is exactly like liver, but both are organ meats and have a lot of similarities.
I haven't cooked kidneys myself but I have had more than one steak and kidney pie as well as other people's family favorites like broiled lamb kidneys.
My hubby is trying to expand his world of food and has agreed (after a decade of saying no) to try some more things. Recently I cooked a package of chicken livers for the first time for him (I always cook the chicken or turkey livers that come with the birds for myself). He manfully ate them but said no, it wasn't going to be a big favorite. He will eat liverwurst maybe once a year or so. Sadly for me because I love braunschweiger but since I was diagnosed with too much iron in my blood I am supposed to stay away from liver. I looked up kidneys and apparently they are ok iron-wise.