Blackcrown is on or near the coast just north of Whispering Sound. The only members of the house to appear or be mentioned are Lord Jon Bulwer, who was wed to Victaria Tyrell who is a cousin to the main branch of the Tyrells, their young daughter Lady Alysanne, and Black Jack Bulwer of the Night’s Watch. Their motto is, “Death Before Disgrace.”
Information about House Bulwer that reveals spoilers from the books.