Is their a proper noun

Answer 1

The word 'their' is a pronoun called a possessive adjective.
A pronoun is a word that takes the place of a noun in a sentence.
A possessive adjective is a pronoun placed before a noun to describe that noun as belonging to two or more people or things.

Examples:
Jack and Jill are looking forward to visiting their grandparents.
I dropped two eggs and cracked their shells.

A noun is a word for a person, a place or a thing.
A common noun is a general word for any person, place, or thing.
A proper noun is the name of a specific person, place, or thing.

In the example sentences:

• Jack and Jill are both proper nouns, the names of people.
• grandparents is a common noun, a general word for the parents of anyone's parents.

Answer 2

No, "their" is not a proper noun. "Their" is a possessive pronoun used to show ownership or belonging to a group of people.