"Quien es Santos?"
Su hija es hermosa* como usted * Feminine gender, for daughter.
"Whose car is it?"
Whose birthday is it.
"¿De quién es el libro?" translates to "Whose book is it?" in English.
it means: it's (she's) the daughter.
To answer "De quién es?" (Whose is it?), you can respond by saying the owner's name or simply stating "es mío" (It's mine) or "es tuyo" (It's yours) depending on the context.
Son in law is male related to you by marrying your daughter.
es she is, I nfact she is the daughter of al capone
it means: she's Pablo's daughter.
You can say "Mi hija es muy hermosa".
daughter