Which is the correct verb in each of the sentences?

Singular = is
Plural = are

Basic English.

1. Peter is one of the boys who is/are missing.
2. More than one of the boys is/are missing.

I'm confused because I was told by my English tutor that for the first sentence, it should be "are", as Peter is one of the missing boys, notbthtg

Please ignore the earlier reply.

Could someone please help? Please confirm if I am correct or wrong.

This is a tricky one and I'm not sure that I can give you the grammatically correct answer.

We know that some boys are missing and that Peter is one of them. So even though "Peter" is singular, he belongs to the group of "boys who are missing".
This group is plural, and requires "are".

Here are examples:

Vanilla is one of the flavors which are no longer offered.
Pakistan is one of the countries which are known to have nuclear weapons.
A shovel is one of the tools which are helpful when excavating a site.

English speakers use 'are' in those two examples.


The rule of proximity in the topic of subject/verb agreement notes:

When a compound subject contains both a singular and a plural noun or pronoun joined by "or" or "nor," the verb should agree with the part of the subject that is closest to the verb. This is also called the rule of proximity.

Example: The student or the committee members write every day.

Example: The committee members or the student writes every day.

https://academicguides.waldenu.edu/writingcenter/grammar/subjectverbagreement

Thanks.

The examples do no use "or" or "nor," though.

It's right! But could you elaborate on your answer?

https://www.merriam-webster.com/words-at-play/notional-agreement-subject-verb-principle-proximity