You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For simplicity, answers should be in all lower cased letters.

Category: SIBLING REVELRY 
Clue: Dingane became King of the Zulus in 1828 after taking part in the murder of this king, his own brother
shaka

Category: FOREIGN CURRENCY 
Clue: It's the currency used in Curacao
dutch guilder

Category: FRANKLY 
Clue: This Frankish king earned his byname "The Hammer" by beating back the Muslim invasion of France at Poitiers in 732

charles martel