What is verb of sentences the families have been feuding for many years?

The verb in the sentence "The families have been feuding for many years" is "have been feuding".

Here's why:

* "Have been feuding" is a present perfect continuous verb phrase. It indicates an action that started in the past and continues up to the present.

* "The families" is the subject of the sentence.

* "For many years" is an adverbial phrase that tells us how long the feuding has been going on.