The mistake in this sentence is the use of the word "of" is missed between neither and them.
When neither is used in the sentence?
The use of neither is used in a negative manner when both options are not selectable. It helps to make a sentence about two things at the same time.
The sentence missed the use of the word "of", so the correct sentence will be "I've got two cousins who lived in Canada, but neither of them speaks French.
Learn more about negative sentences,here:
https://brainly.com/question/17965175
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