核心问题
It is being repaired by a friend of my father's. (New Concept English, Book 2, L. 10)
a friend of my father's 是否可改为 one of my father's friends?
词典解答
这两个结构的含义是完全相同的。唯一的细微差别，就是 a friend of my father's 没有表示 my father 有一个朋友，还是有许多朋友，而 one of my father's friends 则明确表示 my father 有两个以上的朋友。
I have been talking to a friend of yours. (“one of your friends”) (CGEL) 我一直在同你的一位朋友谈话。