Kamek is one of Bowser's main henchmen and leader of the Magikoopas.
He is the King's left arm and the one that raised him as a child in Yoshi's Island, in this game he decided to kidnap Baby Mario and Baby Luigi to prevent them from becoming a treat in the future schemes of Lord Bowser. Yoshi's Island is set in the past long before the start of the Mario series. After that he reappeared later in the timeline to aid an adult Bowser in his evil plans.
Despite his status of high rank magician from the regular games, in Brutal Mario he just briefly appears in the Crash and Burn sections of Finish! Bowser's Keep as an obstacle, flying into the player on a broom like the final level of Yoshi's Island.