Say I have a gym instructor called Anne and it's her birthday. I want to convey that to someone who doesn't know who Anne is in one sentence.
In speech, I would probably say, "it is Anne, my gym instructor's, birthday." But, in writing, that seems wrong; it puts the possessive "s" in the subclause only.
So what is the correct way to write a sentence like this? "It is Anne's, my gym instructor's, birthday"? "It is Anne's, my gym instructor, birthday"? Something else?