It means. "Who is Sonia's [girl] cousin?"
"De quien" means from who?; "De quien(?)-whose(?)";
"De quien" means "from whom"
Whose.
"De quien" means from who?; "De quien(?)-whose(?)";
It means: from who friend
"Who's from Chicago?"
Whose birthday is it.
Quien es el hilo de mi hermano ---- the person for whom my brother lives
"who's the letter from?"
who binds the rings
"Es la prima de" translates to "she is the cousin of" in English. This phrase is used to indicate a familial relationship in Spanish.
who is your spanish teacher