I heard this the other day, and it struck me as odd — mostly because there is a bad habit among many American children to say “mines” instead of “mine”.
Problem:
A pronoun may not be converted into a possessive simply by adding apostrophe-“s”.
Explanation:
The archaic use of the word “mine” as a pronoun is as a substitute for “my” — as in “Mine eyes have seen the glory …”.
But the word “mine” as a pronoun has two modern meanings:
- a predicate-adjective form of the possessive case of the pronoun “I”, as in “The green car is mine.”;
- something belonging to me, as in “Mine is the purple towel.”
I am unsure whether the “mine” in “a student of mine’s mother” more closely follows definition #1 or definition #2.
Concentrating on the first part of the phrase, one could argue that the “mine” in “a student of mine” follows definition #1 because one could say, “The student is mine.”
Or one could argue that the “mine” in “a student of mine” follows definition #2 because one could say, “Mine is the student.”
No matter which argument makes more sense to you, it is clear that “mine” in “a student of mine’s mother” is a pronoun.
And a pronoun may not be converted into a possessive simply by adding apostrophe-“s”, so the phrase must be rewritten.
Solution:
“the mother of one of my students”
OR
“one of my students’ mothers”