Translation:Are they sisters?
There are no meanings to a kana. It is like you are asking "what is the difference in meaning between e, é, ê and è?" The pronunciation is changed for those small kana where the sound merges with the previous or next kana like this: きゃ ki+ya=kya, ティ te+i=ti, あっち a+tu+chi=acchi
General complaint: why does the audio have to be so fast? In learning to play music, we start slow and increase our speed as we gain mastery. To learn new language, we have to be able to hear and repeat. It makes no sense to go so fast when the new learner is struggling with both word recognition, phrasing, and rhythm.
Please SLOW DOWN!
ぼく is only a little politer than おれ and I would say it is considered "young" (but yes some people consider it as childish). Both ぼく and おれ are used by male. I have only heard a female say ぼく and おれ in anime. So to show respect to people who is not close enough to you, I recommend to use わたし. ぼく can be pluralized as ぼくら (if you heard the manga/anime ぼくらの - literally "our").
For "Are they brothers? (かれらはきょうだいですか？)," we used 'karera' which is 'They (male)'.
However, for "Are they sisters? (かのじょたちはしまいですか？)," we used 'Kanojotachi' which is the pluralized form of kanojo.
Just curious why we used 'Kanojotachi' instead of the 'karera' counterpart: 'kanojora' - They (female).
Does this have to do with politeness, sentence structure, or is it situational socially?