Answer:
"Uncle" is actually a noun.
Step-by-step explanation:
It isn't an adjective because it isn't explain what some(thing)(one)(where) is.
It isn't a pronoun due to the fact that the "7 pronouns" are: the personal pronoun, the demonstrative pronoun, the interrogative pronoun, the relative pronoun, the indefinite pronoun, the reflexive pronoun, and the intensive pronoun. Which uncle fits into none of those.
It isn't an article because an article itself is a noun.
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Hope this helps!