Alecto and Amick Carrow:
They are first mentioned in the sixth book of the Harry Potter series. They, along with several other Death Eaters, have witnessed the death of Albus Dumbledore, who was killed by Professor Severus Snape at Hogwarts. They are then mentioned in the seventh (last) part of the series, when they were appointed teachers at Hogwarts at the request of Voldemort - the Black Lord, so that he could control the school. Alecto Carrow has been appointed a teacher of Nebula Studies in place of Professor Charity Burbage, who was assassinated by Voldemort. Alekto's brother, Amick Carrow, has been appointed a teacher of Defense Against the Black Arts in place of Severus Snape, who becomes director of Hogwarts. At the end of the last part, the two take an active part in the Hogwarts attack, along with the other Death Eaters.