What is the title of an English Duke's son?

Question

This son will become the duke after his father dies.

Answer 1

It depends on whether the Duke has any other subsidary titles, if so his eldest son will take the highest of these, if not then he's known as "Lord" until his father dies. A Marquess is the next highest after a Duke so quite often that's the title, however, it's a courtesy title, not held in it's own right. For example the Duke of Marlborough is also Marquess of Blandford, Earl of Sunderland, Earl of Marlborough, Baron Spencer of Wormleighton and Baron Churchill of Sandridge. Consequently the Duke's eldest son takes the next highest title, Marquess of Blandford and his eldest son takes the title Earl of Sunderland, of course these will all change upon the death of the current Duke.

Answer 2

Duke Dude.

Answer 3

No. 1 son?

Answer 4

The eldest son of a Duke is titled "Marquis" and shall become "Duke" after the death of his father, the Duke.

Younger sons are titled "Lord" and retain that title for life, unless the elder brother dies before the youngers, whereas the next eldest becomes "Marquis" and thereby inherits the title "Duke" upon his father's death.

Etc.etc.etc...