Questions & Answers about Kuka auttaa heidän sukulaistaan?
Why does the word for relative end in -aan here?
Because it has a third-person possessive suffix attached to it. The base word in the partitive case is sukulaista. To say their relative, we add the third-person suffix. Here, we do this by lengthening the final vowel -a and adding -n, which gives us sukulaistaan.
Could we drop the word heidän and just say Kuka auttaa sukulaistaan?
Generally, no. For third-person owners (his, her, their), standard Finnish requires you to use the genitive pronoun like heidän in addition to the possessive suffix. The only time you can drop the pronoun is if the owner is also the subject of the sentence, but here the subject is Kuka (Who).
Why is the base word in the partitive case before adding the suffix?
Because of the verb auttaa (to help). This verb always requires its object to be in the partitive case. The dictionary form of the word is sukulainen, and its partitive form is sukulaista. You must put the word into the correct case before adding the possessive suffix at the very end.
Is it also correct to use the -nsa suffix and say heidän sukulaistansa?
Yes, absolutely! The third-person possessive suffix has two forms: -nsa or -nsä and the vowel lengthening plus -n. Both sukulaistansa and sukulaistaan are grammatically correct. However, when a word already ends in a short vowel, the lengthened vowel version (sukulaistaan) is much more common in everyday use.