Which one is correct?
- It is my friend’s, Adam’s birthday.
- It is my friend, Adam’s birthday.
Does the word ‘friend’ need an apostrophe to show possession?
If using the nonrestrictive (as discussed in another answer), I would simply rephrase the sentence to avoid the possessive:
It’s the birthday of my friend, Adam.
With this, there is no awkward question about where to put the possessive apostrophe. (Because it will look strange no matter where you put it.)