Translation:Are they brothers?
"Kare" means 'he' but "karera" indicates a group of people which consist of NOT ONLY women. For example, there are two guys and a girl standing together. Asking about them, you would use "karera". And yes, the answer siblings is correct. Brothers could be as well but everything depends on the context.
Throughout duolingo, I am having issue with only one of the tiles, for use in answering these types of questions, being capitalized. Without knowing the Japanese I can see which word is going to be first and in questions where the student is to learn the difference between, in this case, 'he' and 'she', then there should be at least two capitalized choices or none. As these lessons continue, and my mind does default to the capitalized word as first, I still have issues later on with the pronouns since I have not really been able to grasp them as well as the other components in Japanese sentences.