Are Nietzsche and Kierkegaard considered existentialists?

I read both of them in my existentialism course. Possibly the single unifying characteristic of those thinkers we call existentialists is their taking subjective human experience as a first principle from which all other philosophy must be drawn. In this respect, the work of both Kierkegaard and Nietzsche clearly form an essential groundwork for later writers. Kierkegaard, who wrote first, is often called the "Father of Existentialism", and, more specifically, Christian existentialism. It could also be said that Nietzsche's work was a major foundational force for atheistic existentialism. Although it's unclear how the ideas of either writer would square with those of 20th century existentialist thinkers, IMO a complete coverage of the doctrine[s] would be incomplete without mention of them. Hope that helps.