Learn Turkish: Sülaleden kimler bize yardım ediyor? - Who all from the extended family are helping us?

Adding the plural suffix -ler to kim shows that the speaker expects the answer to be more than one person. It translates naturally to 'who all' or 'which people'. If they just used kim, they wouldn't necessarily be anticipating a list of multiple helpers.

Since kimler is plural, why is the verb singular (ediyor instead of ediyorlar)?

In Turkish, it is very common to use a singular verb when the subject is a plural question word like kimler or neler. You could grammatically say ediyorlar, but leaving the verb singular often sounds more natural because the specific individuals haven't been identified yet.

What is the difference between sülale and aile?

Aile usually refers to your immediate family or household. Sülale refers to your extended family, relatives, or even your ancestry. In this sentence, it emphasizes asking who from the wider network of aunts, uncles, and cousins is stepping up to help.

Why does the sentence use the dative bize instead of the accusative bizi for 'helping us'?

The compound verb yardım etmek literally means 'to do help'. In Turkish, you don't 'help someone' using the direct object accusative case; instead, you 'do help to someone'. Therefore, the receiver of the help must take the dative case, turning biz into bize.