My cousin is one of those people who (love, loves) to eat pizza.
According to the rules of grammar, the relative pronoun "who" refers to the plural noun "people". Therefore, the correct verb choice is "love".
However, in reading the meaning of the sentence as constructed i.e. "My cousin is people who love to eat pizza." An awkward arrangement used to satisfy the rule that the pronoun agrees with the nearer noun.
Notice that if the relative pronoun "who" refers to the indefinite pronoun "one" then the meaning of the sentence reads "My cousin is one who loves to eat pizza."
Question: Why can't the sentence use "loves" instead of "love"?