Stephen Dedalus is the protagonist of Joyce's semi-autobiographical novel, A Portrait of the Artist as a Young Man. In effect, Stephen is the name Joyce chose for himself.
Stephen Tennant (1906-1987) was a louche British aristocrat who was said to spend most of his time in bed. Some of that horizontal time was spent with the war poet Siegfried Sassoon, with whom he had a four-year relationship. Tennant is thought to have been a model for Evelyn Waugh's Sebastian Flyte in Brideshead Revisited.
Stephen Spender (1909-1995) was a British poet and author who fought on the Republican side in the Spanish Civil War. Like Tennant (but not Dedalus), he was bisexual.