Whose

Most languages make the relative pronoun whose agree with either the possessor or the thing possessed. To the first group belong German, Dutch, Swedish, Czech, Polish, among others; to the second, Portuguese, Spanish, Italian, etc.

Group 1:
German: Die Mütter, deren Kinder in dieser Schule lernen, sind unzufrieden.
Dutch: De moeders wier kinderen in deze school leren zijn ontevreden.
Swedish: De mödrar vilkas barn lär sig på denna skola är missnöjda.
Czech: Matky, jejichž děti se učí v této škole, jsou neuspokojeny.
Polish: Matki, których dzieci uczą się w tej szkole, są niezadowolone.
Russian: Матери, дети которых учaтся в этой школе, недовольные.

Group 2:
Portuguese: As mães cujos filhos estudam nesta escola estão insatisfeitas.
Spanish: Las madres cuyos hijos estudian en esta escuela están insatisfechas.
Italian: Le madri i cui figli studiano in questa scuola sono insoddisfatte.

By looking at that, one might think that Germanic and Slavic languages follow group 1 and Romance languages, group 2, but that is not always the case. Romanian, a Romance language, belongs to both groups 1 and 2, since two kinds of agreement must take place, with the possessor and the thing possessed:

Mamele ai căror copii se învaţă în această şcoală sunt nesatisfăcute, where ai agrees with copii (masculine plural) and căror agrees with mamele (feminine plural). By the way, the mother of all Romance languages, Latin, actually follows group 1, not 2!

Matres quarum filii in hac schola student contentae non sunt.