I have a question

[subdolus]

Good day

I have a question. Are these sentences correct?

1. An uncle of Mark's.
2. An uncle of Mark.

[Harry Smith]

Good day

I have a question. Are these sentences correct?

1. An uncle of Mark's.
2. An uncle of Mark.

Both are incorrect: "Mark's uncle " is correct.

[subdolus]

To Harry Smith
Are you sure?

[BobK]

Good day
I have a question. Are these sentences correct?
1. An uncle of Mark's.
2. An uncle of Mark.

Yes "Mark's uncle" is correct. But form 1) is widely used colloquially. And when you're using a pronoun, it's even more common.

The phrase "an uncle of mine" doesn't mean the same as "my uncle"; if you want to avoid the "mine", you have to come up with some periphrasis like "one of my uncles, of which I have several". I have no problem with the possessive here.

(Incidentally, they're not sentences )

b

[Harry Smith]

To Harry Smith
Are you sure?

Thanks to BobK. He explained you instead of me.