intfiction.org

I think that in "Uncle Oren," "Uncle" is functioning almost as a title, and so is capitalized, as Kevin has stated, as effectively part of the name. In "your uncle Oren," it performs a different function -- almost as an adjective modifying "Oren" -- so Capmikee is correct that upper-case would be inappropriate for that usage.

Robert Rothman (self-proclaimed head of the language police)

Ok. I'll name him 'plain Mr. oren'.

Right. In this case, "Oren" is an appositive noun, and it's being used restrictively. That is, if you only have one uncle, then "your uncle, Oren, is standing here" would be correct, but the commas are often omitted around short appositives of this sort. However, if you have two or more uncles, then "your uncle Oren is standing here" would be the only correct punctuation. "Uncle" is capitalized when it's part of a noun of address, as in, "Hey, Uncle Oren -- want a snack?"

Similarly, "I saw Mother this morning," or "I saw my mother this morning." Both are correct, and changing the capitalization in either sentence would be wrong.