I don't care if this one is true or not, or even if chunks of it were ripped from Greek mythology.
Julian was a well-connected nobleman who married a wealthy widow. Let's round the story out to say that she was young and beautiful as well. He was out hunting and, like many hunters in those days, received a prophecy from the stag he had run down. The bucks in North America don't predict anything to the hunters, but apparently they shared their auspicious gifts freely in medieval Europe. This particular stag warned that Julian would one day kill his parents; presumably Julian allowed his quarry to depart unscathed in exchange for this admonition.
Without any explanation, Julian took his wife and moved far away. His parents, disconsolate at his precipitous flight, tracked him down for a surprise visit. He was out hunting again when they arrived, but his wife thoughtfully invited them to rest in the master bedroom. He came home, and finding two bodies in his bed, flew into a jealous rage. After killing the people he mistook for his wife and her lover, he pulled off the covers and discovered his parents.
He took his winsome, wealthy wife with him and went to Rome, seeking penance. He wasn't sure he had earned forgiveness just by sightseeing in the Holy See, so they built a riverside hospice on the way home. They also stayed their awhile so Julian could row folks across the river so they could stay at the hospice.
One visitor was so wretched, a half-frozen leper, that our saint invited him to sleep in Julian's own bed. No word about the saintly wife's reaction, but the leper was of course an angel in disguise who assured Julian that his forgiveness had been granted by the Lord.