Meanwhile, the Crovan dynasty had retained the title "king of the Isles" and control of Lewis, Harris, and the Isle of Man. After a few decades, they acknowledged the English kings as their overlords, so Dougall's heirs (the MacDougalls) complained to Haakon, the Norwegian king, and in 1237 were rewarded by the kingship being split; rule of the Hebrides was transferred to the MacDougall line, and they were made the "kings of the Hebrides". They established the twin castles of Aros (in Mull) and Ardtornish (on the mainland, opposite), which together controlled the Sound of Mull.