The Blackwoods are an old house in the riverlands, descended of the First Men, and are perhaps the only remaining great house of riverlords which follows the old gods. The Blackwoods have been feuding with the Brackens for nearly a hundred years after Lord Quentyn Blackwood was killed during a melee by Ser Otho Bracken, called the Brute of Bracken. Tytos Blackwood is the lord of the house.
Lord Tytos has a son, Lucas, but whether he is his heir and has any siblings remains a question.
Information about House Blackwood that reveals spoilers from the books.