Translation:They are the names of Kateřina's brothers.
Hi, I tried that translation and it accepted, but it said that there was a typo in it, and the typo was the apostrophe. It said that the correct translation was without the apostrophe. I just realised that this typo warning always occurs with the possessive plural nouns in other sentences as well, even if at the top of the discussion page the translation correctly contains the apostrophe. This must be a general error of the platform.
Anyway, thanks for your quick responses, I can see that you actively respond to posts and consider suggestions immediately. This is exceptional and does not usually occur with other Beta courses (sometimes we have to wait for months until a suggestion is taken into account).