A person becomes a grandma or a grandpa, a grandmother or a grandfather, when their son or daughter has a child. The term grandma or grandpa is a common noun naming a specific role a person plays in life. These common nouns do not get capitalized.
When a person’s brother or sister has a child, that person becomes an aunt or an uncle. Once again, the terms aunt and uncle are common nouns naming a specific role that people play in life.
John’s uncle is a doctor.
I visited my grandmother yesterday.
Susan likes being a grandma.
However, when we call that person by name, we are using a proper noun. Therefore, anytime your are addressing your grandmother or grandfather or aunt or uncle by name, you must capitalize the word. That term for their relationship with you becomes a proper noun. Look at these examples:
Grandma, I’ll come mow your lawn on Saturday.
Mary and I are visiting Aunt Betty tomorrow.
Grandpa Dan and I are going fishing this weekend
The terms grandmother, grandma, grandfather, grandpa, aunt and uncle are common nouns and should not be capitalized unless they are being used to address that person by name.
▶It’s your turn. Decide if any words in this sentence should be capitalized. Sam’s uncle is a truck driver. Did you figure out that there are no proper nouns in this sentence? Good for you!