Is a ferret related to a stoat?

I don't think so, but ferrets can interbreed with wild polecat ferrets. In Russia, a hybrid was created of a ferret and a European mink, named "Khonorik". Its parents were a hybrid male of a polecat ferret (wild x steppe) and a female of European mink, making it a hybrid of three species. Later on Khonoriks were bred from a thoroughbred wild European polecat ferret and European mink.