Can Dearest Be Plural?

Plural form of dearest.

Is it correct to say my dearest?

Dear is usually used to address people at the start of a letter or email (Dear Mr. Smith) or as a pretty formal way to regard someone in conversation, however, it's usually only used by the upper class and elderly. Dearest is used as a form of address too, but often goes with people you care deeply for.

Can Dearest be a noun?

dearest used as a noun:

A beloved person; a term of endearment.