[Grammar] Cousin conundrum

[suzieuda]

I was listening to a song and it had the following lyrics:

"I was a friend of your cousin"

Is this correct or should it be "I was a friend of your cousin's"?

Thanks!

 

[Raymott]

I was listening to a song and it had the following lyrics:

"I was a friend of your cousin"

Is this correct or should it be "I was a friend of your cousin's"?

Thanks!

You can say either.