or vice versa.
Paul Lafargue is maybe the prime example.
Judah Grossman-Roshchin (1883-1934) is an interesting case. From what I've gathered he was an anarchist from his teens up to and until working with Makhno in the Ukraine. Afterwards he critiqued anarchists such as Kropotkin and was in general busy with the history and theory of anarchism, but also literature from a Marxist perspective. Hopefully someone like battlescared could put up a biography in the library.